How to process models while using tobspr's RP?

Yes, you can write code to create RP materials. However, I repeat, you need to study the models again. And these sections:

Manual

https://docs.panda3d.org/1.10/python/programming/texturing/index
https://docs.panda3d.org/1.10/python/programming/render-attributes/materials

API

https://docs.panda3d.org/1.10/python/reference/panda3d.core.Texture
https://docs.panda3d.org/1.10/python/reference/panda3d.core.TextureStage
https://docs.panda3d.org/1.10/python/reference/panda3d.core.Material

This way you can find out the initial parameters of the models that come with RP. Please note that the order of the stages for textures is important.

from direct.showbase.ShowBase import ShowBase
from panda3d.core import MaterialAttrib, TextureAttrib

class App(ShowBase):
    def __init__(self):
        ShowBase.__init__(self)

        scene = loader.load_model("Scene.bam")

        for node_path in scene.find_all_matches('**/+GeomNode'):
            geom_states = node_path.node().get_geom_states()
            print(node_path.name)
            for geom_state in geom_states:
                if geom_state.has_attrib(MaterialAttrib):
                    print(geom_state.get_attrib(MaterialAttrib).get_material())

                if geom_state.has_attrib(TextureAttrib):
                    texture_stages = geom_state.get_attrib(TextureAttrib).get_on_stages()
                    for texture_stage in texture_stages:
                        print(texture_stage, geom_state.get_attrib(TextureAttrib).get_on_texture(texture_stage))

                print("------------------------")
app = App()
app.run()

out:

2.003
Material
  base_color = 0.195987 0.195987 0.195987 1
  refractive_index = 1.38467
  emission = 0 0 0 0
  roughness = 0.629749
  metallic = 0
  local = 0
  twoside = 0

TextureStage empty_basecolor-0, sort = 0, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_basecolor.png (from /d/Code/RenderPipeline/test/scene/tex/empty_basecolor.png)
  2-d, 2 x 2 pixels, each 3 bytes, srgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

TextureStage empty_normal-10, sort = 10, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_normal.png (from /d/Code/RenderPipeline/test/scene/tex/empty_normal.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_specular-20, sort = 20, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_specular.png (from /d/Code/RenderPipeline/test/scene/tex/empty_specular.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_roughness-30, sort = 30, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_roughness.png (from /d/Code/RenderPipeline/test/scene/tex/empty_roughness.png)
  2-d, 2 x 2 pixels, each 3 bytes, rgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

------------------------
1.002
Material
  base_color = 1 1 1 1
  refractive_index = 1.5
  emission = 0 0 0 0
  roughness = 0.3
  metallic = 0
  local = 0
  twoside = 0

TextureStage BackDiff-0, sort = 0, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture pattern.png (from /d/Code/RenderPipeline/test/scene/tex/pattern.png)
  2-d, 128 x 128 pixels, each 4 bytes, srgb_alpha
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  65536 bytes in ram, compression off

TextureStage empty_normal-10, sort = 10, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_normal.png (from /d/Code/RenderPipeline/test/scene/tex/empty_normal.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_specular-20, sort = 20, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_specular.png (from /d/Code/RenderPipeline/test/scene/tex/empty_specular.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_roughness-30, sort = 30, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_roughness.png (from /d/Code/RenderPipeline/test/scene/tex/empty_roughness.png)
  2-d, 2 x 2 pixels, each 3 bytes, rgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

------------------------
3.003
Material
  base_color = 0.486 0.631 0.663 1
  refractive_index = 1.40974
  emission = 0 0 0 0
  roughness = 0.0544803
  metallic = 0
  local = 0
  twoside = 0

TextureStage empty_basecolor-0, sort = 0, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_basecolor.png (from /d/Code/RenderPipeline/test/scene/tex/empty_basecolor.png)
  2-d, 2 x 2 pixels, each 3 bytes, srgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

TextureStage empty_normal-10, sort = 10, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_normal.png (from /d/Code/RenderPipeline/test/scene/tex/empty_normal.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_specular-20, sort = 20, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_specular.png (from /d/Code/RenderPipeline/test/scene/tex/empty_specular.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_roughness-30, sort = 30, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_roughness.png (from /d/Code/RenderPipeline/test/scene/tex/empty_roughness.png)
  2-d, 2 x 2 pixels, each 3 bytes, rgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

------------------------
3.002
Material
  base_color = 0.486 0.631 0.663 1
  refractive_index = 1.40974
  emission = 0 0 0 0
  roughness = 0.0544803
  metallic = 0
  local = 0
  twoside = 0

TextureStage empty_basecolor-0, sort = 0, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_basecolor.png (from /d/Code/RenderPipeline/test/scene/tex/empty_basecolor.png)
  2-d, 2 x 2 pixels, each 3 bytes, srgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

TextureStage empty_normal-10, sort = 10, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_normal.png (from /d/Code/RenderPipeline/test/scene/tex/empty_normal.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_specular-20, sort = 20, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_specular.png (from /d/Code/RenderPipeline/test/scene/tex/empty_specular.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_roughness-30, sort = 30, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_roughness.png (from /d/Code/RenderPipeline/test/scene/tex/empty_roughness.png)
  2-d, 2 x 2 pixels, each 3 bytes, rgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

------------------------
1.001
Material
  base_color = 1 1 1 1
  refractive_index = 1.5
  emission = 0 0 0 0
  roughness = 0.3
  metallic = 0
  local = 0
  twoside = 0

TextureStage BackDiff-0, sort = 0, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture pattern.png (from /d/Code/RenderPipeline/test/scene/tex/pattern.png)
  2-d, 128 x 128 pixels, each 4 bytes, srgb_alpha
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  65536 bytes in ram, compression off

TextureStage empty_normal-10, sort = 10, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_normal.png (from /d/Code/RenderPipeline/test/scene/tex/empty_normal.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_specular-20, sort = 20, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_specular.png (from /d/Code/RenderPipeline/test/scene/tex/empty_specular.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_roughness-30, sort = 30, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_roughness.png (from /d/Code/RenderPipeline/test/scene/tex/empty_roughness.png)
  2-d, 2 x 2 pixels, each 3 bytes, rgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

------------------------
2.002
Material
  base_color = 0.195987 0.195987 0.195987 1
  refractive_index = 1.38467
  emission = 0 0 0 0
  roughness = 0.629749
  metallic = 0
  local = 0
  twoside = 0

TextureStage empty_basecolor-0, sort = 0, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_basecolor.png (from /d/Code/RenderPipeline/test/scene/tex/empty_basecolor.png)
  2-d, 2 x 2 pixels, each 3 bytes, srgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off

TextureStage empty_normal-10, sort = 10, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_normal.png (from /d/Code/RenderPipeline/test/scene/tex/empty_normal.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_specular-20, sort = 20, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_specular.png (from /d/Code/RenderPipeline/test/scene/tex/empty_specular.png)
  2-d, 2 x 2 pixels, each 4 bytes, rgba
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  16 bytes in ram, compression off

TextureStage empty_roughness-30, sort = 30, priority = 0
  texcoords = texcoord, mode = modulate, color = 1 1 1 1, scale = 1, 1, saved_result = 0, tex_view_offset = 0
 2d_texture empty_roughness.png (from /d/Code/RenderPipeline/test/scene/tex/empty_roughness.png)
  2-d, 2 x 2 pixels, each 3 bytes, rgb
  sampler wrap(u=repeat, v=repeat, w=repeat, border=0 0 0 1) filter(min=linear_mipmap_linear, mag=linear, aniso=16) lod(min=-1000, max=1000, bias=0)  12 bytes in ram, compression off
...