Using a very sharp knife, lop off the top ½” of each head of garlic—exposing most of the cloves.
Place the head of garlic, root side down, in a shallow baking dish (a loaf pan usually does the trick). Season liberally with salt and pepper.
Cover the dish tightly with aluminum foil, and then bake in preheated oven for 35-40 minutes, or until the garlic cloves are very soft and mushy.
To remove the roasted garlic, wait until the heads are cool enough to handle, then squeeze the heads upside down over top of a bowl. The roasted garlic should easily squeeze out of the peel.