Without individually separating the rolls, cut them horizontally in half. Place the bottom half in a greased 9x13 inch baking pan.
Then layer the bottom of the rolls with the ham, Swiss cheese, and pickle slices. Then place the top portion of the rolls to form the sandwich.
In a bowl, combine the melted butter, grated onion, and mustard.
Brush or drizzle the butter over the top of the rolls.
Cover with foil and bake at 350°F for 10 minutes, then uncover and bake 5-10 minutes longer or until golden brown and cheese is melted.
Remove from pan and cut into individual sliders and rolls.