Hi Schnuer - welcome to the cove!
I use a Pocket Surf portable roughness gauge for measuring machined brass and stainless steel. We only use the Ra scale.
Here is the current model, ours is older: http://www.mahr.com/index.php?NodeID=2410
It's an old gauge, but it's held up to being used by many people, many times a day - all of our operators, set up guys, QC inspectors, and R&D people used it multiple times on a daily basis. We keep it on a stand in the QC office.
If you use it heavily expect to replace the probes fairly frequently as they will see the most abuse. We replace ours every 6 months.