Make the sauce by combining the warm melted butter with the Dijon mustard, poppy seeds, brown sugar, Worcestershire sauce, garlic powder, and onion powder. Whisk well, and set aside to let the flavors mingle.
Preheat the oven to 350 degrees. Spray a cast-iron skillet with olive oil cooking spray.
Split the rolls in half (top & bottom). Spread mayonnaise on the bottom halves to taste.
Place a few pieces of ham on the bottom halves, then top with Swiss cheese.
Put the roll tops on top and place them in a single layer in the cast-iron skillet.
Whisk the butter sauce until thick and well combined.
Brush the mixture over the rolls.
Cover with foil and bake for 20 minutes.
Remove the foil and bake for 5 more minutes. Serve and enjoy!