Preheat the oven to 350℉ and spray a 9 x 13 baking dish with a non-stick cooking spray. Then, set aside.
In a large skillet over medium-high heat, add the ground beef to the skillet. Cook for 6-8 minutes or until browned, breaking up the ground beef with a spatula.
Add onions and green peppers and cook for 4-5 minutes or until they become soft. Then, drain off excess grease.
Add tomato sauce, ketchup, brown sugar, mustard, chili powder, Worcestershire sauce, black pepper, salt, onion powder, and paprika. Stir until combined and simmer uncovered for 6-8 minutes or until the sauce thickens.
Slice the Hawaiian rolls in half at once (without separating them). Carefully remove the top half and set it aside. Place the bottom half in the prepared baking dish.
Spread out 1 cup of cheese and top with sloppy Joe mixture. Then, top with remaining cheddar cheese
Place the top half of the rolls over everything.
In a small bowl, add butter and garlic powder. Mix until well combined, then brush on top of the rolls.
Cover with aluminum foil and bake for 15 minutes. Remove the foil and bake for 10 minutes or until the tops are golden brown.
Slice before serving, and enjoy!