Cut rolls in half and line the bottom of baking pan with the bottoms of rolls. Layer the ham slices then cheese then place the top half of rolls back on. Mix together the butter, worchestshire, mustard, brown sugar, and onion powder. Pour the whole mixture over buns, drenching each one. Cover tightly and marinade 4-24 hours. Preheat oven to 350 degrees. Bake 15 minutes uncovered or until cheese is melted and bun tops are quite golden.