The bunny roaster is one of the Barbarian NPCs. He's found in Harrogath, just to the southwest of Larzuk's forge, with this cute little white rabbit on a spit. The bunny roaster is beautifully animated, with one hand turning a lever that makes the spit rotate, while the other smoothly fans the fire beneath the hare, to ensure the meal will be a delicious, evenly-browned delight.
It's only natural; the city is under siege, food is growing short, and there are plenty of hopping bunnies on the surface areas of Act Five. Presumably they taste a fair site better than demon steak?