How to simulate the Surface roughness for a solid particle

I want to simulate how the liquid to wet solid particle by considering the capillary force and surface roughness. I have simulated the capillary force by level set. but for the surface roughness, I have no idea to set the surface roughness.can I simulate the surface roughness by level set as well?
my model is a droplet falling to a sphere solid particle. the water should retain on the surface of the particle by considering the surface roughness. someone can give some ideas?