Your roughness 3D model is stretching usually because of incorrect UV unwrapping (the 2D layout of the model’s surface) or mismatched texture scaling (map size vs. model proportions).
UV unwrapping converts 3D surfaces to 2D for textures—if UVs are distorted or overlapping, roughness details stretch. Mismatched scaling means the map’s size doesn’t fit the model, so roughness looks unnatural instead of matching the shape.
To fix it, relax/rearrange UVs in a tool like Blender’s UV Editor or adjust the texture’s scale in your 3D software to align with the model’s dimensions.