Using a sharp knife, cut the crusts off of each slice of bread. Roll each slice with a rolling pin to flatten. Sprinkle with cheeses and place 6 slices of pepperoni on top. Roll up tightly, seal with a dab of water if needed. Repeat with remaining bread slices, cheese and pepperoni.
Place 1 tablespoon of butter in a large non-stick pan and set over medium heat.
Melt remaining 2 tablespoons butter in a bowl. Dip one roll up at a time in the melted butter, then transfer to the pan. Cook for 1-2 minutes per side or until golden brown and crisp on the outside. Remove and serve with sauce, if desired.
Notes
-You can easily switch out the pepperoni and mozzarella for cheddar and ham!