Cut rolls in half and spread bottom half of rolls with horseradish sauce.
Layer ham on top of horseradish and then layer cheese on top of that.
Replace top half of the rolls on the layered ham and cheese, and place in a large baking dish.
Whisk together mustard, butter, onion powder and Worcestershire sauce and drizzle over rolls.
Sprinkle with poppy seeds. Cover with foil and let sit for fifteen minutes.
Bake at 350 degrees for 8 minutes, remove foil and cook for another 2 minutes until browned. Serve.