LOL now you got me thinking, motorized car rotisserie!
I think the most robust solution and of course most common, would be a 100:1 worm gear drive with a 1750rpm furnace motor (which I have) and a decent ratio pulley drive to run it all. Im sure I can find a reducer for ~120 or so.
I am however thinking in the future of adding an rc setup to the actually chassis of the roaster, that way I can just drive it up into my trailer and off to where ever I want, now that would be sweet!
if you make an RC roaster, grab a scooter motor ! http://www.thesuperkids.com/scmococoki.html have a RC trailer full of lipos. Ive put 500+ miles on that schwinn s1000 w/rear wheel one ! That $349 brushless bad boy would make mincemeat out of the cops in the park.