Preheat oven to 350°F. Cut off the top 1/4-inch of the garlic to expose the cloves. Place garlic on a piece of aluminum foil. Drizzle with oil and sprinkle with nutmeg. Wrap tightly in foil.
Bake 1 hour or until garlic is soft. Cool slightly before unwrapping. Squeeze roasted garlic from skin.
Stir 1 tablespoon of the roasted garlic into hot prepared mashed potatoes.