Hobby Engineering has a bunch of gearmotors...

http://www.hobbyengineering.com/SectionM.html#IX1415

I bought three to remote my tuner. Plenty of torque to turn the caps
and inductor switch in a "1500W" MFJ tuner. They're only $5.50 apiece
new.

They're also all-plastic gearboxes and output shafts, so you don't have
to worry about insulating shaft couplers, etc.

My gut feeling is that the ones I bought (Gear Motor 9: Right Angle
Shaft) could be a bit undersized to turn a roller inductor, especially
since you probably want to go a bit faster.

http://www.n3ox.net/projects/servo has info about my remote tuner.

73,
Dan
N3OX