The first step is to preheat the oven to 375 degrees F. Then line your 9x13 baking dish with tin foil and spray with cooking spray. Trust me, use the tin foil. It will make cleanup so much easier.Slice the Hawaiian Sweet Rolls in two while keeping them together. So you will have two large slabs. Using a serrated knife works best. Place the bottom slab of rolls into the pan you prepared.Pour the pizza sauce over the bottom rolls. Be sure to spread the sauce evenly over the rolls.Use about 1/2 C of the Mozzarella cheese and spread it evenly over the rolls.Place an even layer of pepperoni on top of the cheese.Use the remaining Mozzarella cheese and spread over the pepperoni.Add the top layer of rolls.In a microwave-safe bowl melt the butter. Stir in the onion, parmesan cheese, oregano, garlic powder, salt, and pepper. Brush this mixture on top of the buns.Cover with tin foil, be sure to leave room at the top so the cheese does not stick to it. Let it sit for about 5-10 minutes before putting the pan in the oven.Bake for 12-16 minutes on the middle rack. You may need to go a little longer if your cheese is thick, be sure that all the cheese is melted.Slice into individual sliders and serve. These are best warm right out of the oven.