Preheat oven to 400 degrees F. Rub off excess papery skin from the garlic head without separating the cloves. Slice about 1/2 inch off the top of the garlic head. Place the garlic on a square of aluminum foil or in a ceramic garlic roaster, if you have one. Sprinkle with 2 teaspoons water and pinch the edges of the foil together to make a package.
Roast until the cloves are very soft, 40 to 45 minutes. Unwrap and let cool slightly. Squeeze the cloves out of the skins.