How to make a Rough Surface in 3-d Mesh part?

This is my code,

clc
 clf
model = createpde;
importGeometry(model,'CLAMP PLATE.stl');
pdegplot(model,'FaceLabels','on','EdgeLabels','on')
mesh = generateMesh(model,'Hmax',0.5)
figure
pdemesh(model,'NodeLabels','on')
hold on

In this code i imported a part in which in its second Face i like to make rough Surface by changing its node height but I dont have any idea to proceed further. So, Please help me to solve this problem.

And Thank you in Advance.