To heat up a marshmallow by piercing it with a stick or rod and holding it over a fire (usually in a campfire or fireplace) or other source of heat. The heat causes the sugars in the marshmallow to burn on the outside and become soft and gooey on the inside. Overdoing it can cause a marshmallow to blacken and become burnt. It may also catch flame if it's too close to a fire. A roasted marshmallow is a main ingredient found in s'mores, alongside chocolate and graham crackers.