Preheat the oven to 350 degrees F. Line a 13x9 pan with foil, allowing some to overhang, so you can pull the finished sliders out.

Cut the rolls in half and place the bottoms in the pan.

Fold a slice of roast beef onto each roll.

Cover with a single layer of Swiss cheese.

Combine the melted butter and onion soup mix in a bowl. Pour over the rolls. Cover with foil and let set for 10 minutes.

Bake in the preheated oven for 10 minutes. Remove the foil and cook for 5 more minutes.

Lift the foil out of the pan, and serve warm.