CFD - Surface roughness

Hey guys

I really need your help on this one!

I was wondering if any of you could tell me about the default settings of surface roughness's in COMSOL?
All I've found about it in the documentation is Materials 3D Model Default Appearance Settings but I can't find anything about the use of surface roughness in the calculation of the pressure loss.
But the surface roughness does have an impact on the pressure loss however, I don't know where to find it nor do I know how to change it? Does COMSOL even use the material surface roughness or is it like Blasius --> surface roughness = 0?

Best Regards

Mikael