Combine the olives, rosemary, and red pepper flakes in the center of 1 or 2 large sheets of aluminum foil. Fold the foil to enclose the olives in a pouch. (Recipe can made to this point 1 day ahead, Refrigerate.) Heat oven to 400º F. Bake for 30 minutes. Serve warm.
Note: Heating up olives with herbs and spices is an easy upgrade of a familiar party food, and it perfumes the house with a heady, exotic aroma.