the rollers that go on a conveyor belt system are really cheap from a castor and wheel supply place, and they have bearings in them already_ set them the right distance apart with a 4x36" 180gr sanding belt being your feed belt.
, as for a low speed motor to drive it, i would use a windscreen wiper motor used from the wreckers- we used to use them as the motor on our sheep and pig roasting spits- they last forever- lots of torque- hook up to a 12v battery.- or transformer.
set up a pulley system to power the one roller/
easiest way i can think of