Prepare the Roast Garlic. Heat oven to 375° F.
Cut about ½- inch from the top of 3 garlic heads, exposing the individual cloves. Place the garlic heads on a piece of aluminum foil. Drizzle each head with about 1 teaspoon olive oil. Seal the foil around the garlic making a packet.
Place the foil packet on a baking sheet. Roast until the garlic is soft, about 45 minutes. Remove garlic from the oven and set it aside to cool slightly.
Make the Garlic Bread. Increase oven temperature to 400°F
In a separate bowl, stir one stick (half cup) butter until smooth and spreadable. Add the mashed garlic and stir until smooth. If using, add ½ cup parmesan, 2 tablespoons chopped fresh parsley, and/or a pinch of red pepper flakes. Stir to combine.