Not sure about the Griffin Powermate but you might want to take a look at this thread. I think I am going to get one of them soon.
I know that the Griffin Powermate USB Knob can be configured to scroll though things like playlists, but can it be used to navigate and select the different menu buttons on the Road Runner FE with the DigitalFX skin (instead of clicking on the touchscreen with the finger)?
I bought a Contour Shuttlepro off EBay for around $40, and configured it to work with RR. It took some doing, but now I can do just about everything with it. If you are looking for a hands-off approach to controlling RR, I can thoroughly recommend it.