In a small saucepan, melt margarine. Add mustard, Worcestershire sauce, poppy seeds, and onion flakes. Stir well. Heat until ingredients are melted.
Split rolls open and spread 1 teaspoon of sauce on inside. Layer one slice of ham and one slice of Swiss cheese on each roll. Place rolls in a shallow baking pan and pour remaining sauce over top. Bake at 350° until lightly browned, approximately 10-15 minutes.