Step 1: Preheat your oven to 350°F (175°C). Lightly grease a 9x13 inch baking dish.
Step 2: Using a large serrated knife, carefully slice the entire block of Hawaiian rolls horizontally through the middle, keeping them connected. Place the bottom half of the rolls into the prepared baking dish.
Step 3: Evenly spread half of the pizza sauce (about 1/4 cup) over the bottom layer of the rolls.
Step 4: Layer half of the shredded mozzarella cheese (about 3/4 cup) over the sauce.
Step 5: Arrange all of the pepperoni slices evenly over the cheese layer.
Step 6: Spread the remaining pizza sauce (about 1/4 cup) over the pepperoni, then top with the remaining shredded mozzarella cheese (about 3/4 cup).
Step 7: Carefully place the top half of the Hawaiian rolls back over the layered ingredients, aligning them with the bottom half.
Step 8: In a small bowl, melt the unsalted butter. Stir in the minced garlic, Italian seasoning, onion powder, and optional red pepper flakes.
Step 9: Brush the garlic herb butter mixture evenly over the tops of the rolls, ensuring to get into the crevices between them.
Step 10: Cover the baking dish tightly with aluminum foil. Bake for 15 minutes.
Step 11: Remove the foil and continue baking for another 5-10 minutes, or until the tops are golden brown and the cheese is bubbly and fully melted.
Step 12: Remove from the oven and let rest for a few minutes before slicing the sliders apart along their natural seams. Serve warm and enjoy your Pepperoni Pizza Hawaiian Roll Sliders!