the effect of the roughness to the spread of the microwave?

i want to kown the effect of the roughness to the microwave in the shieded structure.for my aplication ,the frequency is 900MH,and if the roughness is 0.0125mm,is there any large effect to the mw

It's not easy to understand what you want say.
Is the Shielded structure a waveguide, or a mirror or what?
generally speaking the roughness play a role smaller that many people thinks.
For a Waveguide the roughness increase lhe loss (not so mutch as you change the metal from Ag to Al). For a mirror a gaussian distributed roughness generate an effect like a scatter (reflect to every direction in a half sphere). The amount of scattered power (the solid angle integral) is:
1-e^-(4*pi*r/(lambda^2))
where e=2.7182... , r= roughness rms, lambda=3E8/Freq(Hz).

next time, please be more explicit.
have a good day