Preheat the oven to 350° F and prepare a 9x13-inch baking dish with cooking spray. Smaller dish can be used as long as all rolls will fit in the dish.
In a mixing bowl, combine the butter, onion, Worcestershire, poppy seeds, and dry mustard. Stir until well blended.
Remove the dinner rolls from the package and split the rolls. If possible, slice through the entire package of rolls to split them in half while leaving them as a whole. Place the bottom half of the rolls in the prepared baking dish, cut side up.
Spread the butter mixture on the bottom half of the rolls.
Layer the sliced ham.
Sprinkle the grated Swiss and Cheddar cheeses on top.
Top with the top half of the dinner rolls.
Bake for 15 minutes or until the cheese is melted.
Brush additional melted butter on top, if desired.