Inflation/Prism layer for rough surface
 

Hello,
I am studying the effect of surface roughness on a performance of centrifugal pump using Ansys. I have used inflation layer in meshing to capture boundary layer near the blade. the height of inflation layer is approx. 1mm. I want to know that can I go with the same inflation layer for all simulations with different values of roughness or I have to change it?

If so how to relate the height of inflation layer to the mean grain size(0-1.25mm for my case) of wall roughness.
thank You,
Regards,:)