Preheat the oven to 375F and slice your hoagie rolls in half lengthwise. Do not cut all the way through. Place them cut side open onto a sheet tray.
Add the softened butter, parmesan, garlic powder, and Italian seasoning to a small bowl and mix to create a garlic butter.
Stir until everything is well combined.
Using a knife, spread the garlic butter over the exposed hoagie rolls evenly.
Place the buttered rolls in the oven and bake them for 5 minutes or until they're lightly toasted.
Cut a piece of cheese in half and place it on the bottom part of the hoagie roll. Repeat with the other rolls.
Add ham, salami, and pepperoni, all in top of the cheese- evenly distributed on all of the sandwiches.
Add the sliced pepperoncini next. Cut another piece of cheese in half and place it on top of the meat. Repeat the layering of cheese and meat with the rest of the sandwiches.
Close the top piece of bread on the sandwiches and place them into a 9x13 baking dish or one similar in size so all the sandwiches fit. Bake them for another 10-15 minutes until the cheese is melted and the sandwiches are warmed through and bread is toasted. Serve immediately and enjoy.