Preheat your oven to 375°F and lightly grease a 9x13 inch baking dish. While the oven heats, finely dice the green bell pepper and onion into 1/4-inch pieces—uniform sizing ensures even cooking. In a small bowl, combine the melted butter with Italian seasoning and set aside for brushing later.

In a large skillet over medium-high heat, add the ground beef and cook, breaking it apart with a spoon as it browns, about 5-7 minutes. Once most of the pink is gone, add the diced bell pepper and onion along with the Montreal steak seasoning and light brown sugar. Cook for another 3-4 minutes, stirring frequently, until the vegetables soften and the beef is fully browned. Drain any excess grease, then stir in the sloppy joe sauce and Worcestershire sauce. Simmer for 2-3 minutes to meld the flavors. I like to taste the filling at this point and adjust seasoning if needed—sometimes I add a tiny pinch of salt to deepen the savory notes.

Remove the Hawaiian roll slab from the package and carefully slice it horizontally in half using a serrated knife—you'll have a bottom half and a top half that stay as one connected piece. Place the bottom half of the roll slab into your prepared baking dish, cut-side up. Spread the warm sloppy joe filling evenly over the bottom rolls, then distribute the shredded mozzarella cheese generously over the filling. Place the top half of the roll slab over the cheese, and brush the entire top surface with the herb butter mixture from Step 1. I like to use a pastry brush here to ensure every roll gets a nice, even coating of butter.

Cover the baking dish tightly with aluminum foil and bake for 20 minutes at 375°F. This allows the cheese to fully melt and the interior rolls to heat through without the tops browning too quickly. After 20 minutes, remove the foil and bake uncovered for 2-3 minutes more to lightly brown the tops and give them a subtle golden finish.