Preheat the Oven: Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper or lightly grease a loaf pan.

Sauté the Veggies: Heat olive oil in a skillet over medium heat. Add onions, bell peppers, and garlic, and sauté for 5–7 minutes until softened. Set aside to cool slightly.

Prepare the Meatloaf Mixture: In a large bowl, combine ground beef, chopped roast beef, breadcrumbs, milk, egg, Worcestershire sauce, soy sauce, salt, pepper, Italian seasoning, and sautéed vegetables. Mix everything until just combined, being careful not to overwork the meat.

Shape the Meatloaf: Transfer the meat mixture to your prepared baking sheet or loaf pan and form it into a loaf shape.

Bake the Meatloaf: Bake for 45 minutes. After 45 minutes, remove the meatloaf from the oven and top with provolone and mozzarella cheeses. Brush the top with melted butter and return the meatloaf to the oven for an additional 10 minutes, or until the cheese is melted and bubbly.

Rest and Serve: Allow the meatloaf to rest for 10 minutes before slicing. Serve with extra provolone and peppers if desired.