RoadRunner can export scenes to the Wavefront OBJ (.obj) file format.
From the menu, select File > Export > Wavefront (.obj).
Set the file destination and click Export.
This code shows an example of a material in an exported Material Library (.mtl) file:
newmtl Grass1 # Material Name illum 2 # Color with specular highlights Ka 1.000000 1.000000 1.000000 # Ambient color matches the diffuse Kd 1.000000 1.000000 1.000000 # Diffuse color Ks 0.039216 0.039216 0.039216 # Specular color Ns 800.200012 # Specular exponent, approximated from the Roughness value Tr 0.000000 # Transparency map_Kd Grass1_Diff.png # Diffuse Map map_bump Grass1_Norm.png # Normal Map map_Ks Grass1_Spec.png # Specular Map