I am using the Artisan 6M roaster. It's electric so you don't have to fiddle with gas bottles and all that, and can hit 5 Lb a shot easily. It will also do as little as 8 Oz per roast as well. With all the stuff it is in that range, but if you just want the roaster, you have your own cooling system / exhaust etc you can get just the roasting part for significantly less.
Over the holidays I think I roasted 45 Lbs of coffee back to back to back with no problems.