Try a dab of JB Bore Cleaner. It's a paste and will actually help lap the roughness out of the barrel. Over time it should stop happening. It may be that Rohrbaughs need a break in like new rifle barrels. In order to break in a new rifle barrel, even a high quality cut rifled barrel here's what I do. I clean the bore after each shot for the first ten rounds. Then I clean it after every 5 rounds for the next 10 and after 10 I do it again. After those 30 rounds it is considered broken in and ready to go.
Cleaning consists of a pass with a patch with bore cleaner, 5 brush strokes and patch it dry...shoot...clean again same way. In a precision rifle I never use the same brush after the first 10 or the second 10 and throw them away. What you are really doing is by shooting and cleaning is lapping all the roughness out.
If you do that with a Rohrbaugh, by the time that range session ends you'll have disassembly down to an art form.