On what scale do you want to determine the roughness?

If it's on a nanometer-scale, AFM would be the tool of choice, but if your sample is strongly curved, tips may lose contact or crash.

Next level would be white-light interferometry, but that requires accurate calibartion for your material or otherwise you will get bogus numbers.

If you get completely coarse, a mechanical profiler would be an option.

Thank you for your response.

The scale level required is in micrometers.

Dear Logesh,

For micrometers scale you can use portable stylus instrument for surface roughness testing which can also be used for curved and cylindrical surfaces. This instruments can measure both Ra and Rz parameters.

You can also use ASTM D7127 standard for this measurement.

Thank you for your response. sir,

Through a portable surface roughness testing machine, the roughness of curved surfaces can be able to take it properly