Yea what I meant are these things that people use not as actual resistance, but it's like a massage for the muscles and soft tissue, they roll it over the area.

It's usually used for the legs since they've got a lot more portruding larger muscles. It'd probably be tough to do this on the forearm not only because you can't use 2 hands to guide it, but also because the muscle doesn't portrude as much. You have those 2 bones that crosover when you pronate/supinate and stuff.