[BrianG]

For the speed final required, pretty much any motor should work since it will be geared quite low. I am assuming here that you don't need to roast a WHOLE pig. A whole pig is HEAVY and could be difficult to turn without making sure it is balanced and there are bearings on the end.

How about an old washing machine motor, refrigerator compressor motor, fan motor (dekstop size) or something similar? Whatever you get, make sure it is rated for continuous duty, not intermittent duty.

And even if you don't get the exact speed you want, get it as close as possible with gearing and then use a dimmer control to tweak it. You'll need a dimmer capable of driving an inductive load though, and one with a decent rating, but it should be easy to find at Menards, Home Depot, Lowe's, etc.