Preheat the oven to 350 degrees F.
Melt the butter in a microwave safe dish. Whisk in the mustard, honey, poppy seeds, minced onions, salt and red pepper flakes.
Split the rolls. Place the bottom half of the rolls in a shallow casserole dish in a single layer.
Use a pastry brush to coat the bottoms of the rolls with the butter sauce.
Top each bottom with ham and Swiss cheese.
Brush the cheese with a little more sauce. Top the cheese with the top half of the rolls.
Brush the tops of the rolls with the remaining sauce.
Spray a piece of foil with cooking spray. Place the foil over the sandwiches, cooking spray side down. Allow to sit for about 10 minutes.
Bake the tray of sandwiches for about 15 minutes, or until the cheese has melted. Serve the sandwiches warm.