Preheat an oven to 350 degrees F (175 degrees C).
Combine ground beef, onion, green pepper, crackers, and egg in a large bowl.Season with Worcestershire sauce, garlic, seasoned salt, and pepper; mix well. Form mixture into 8 meatballs. Place meatballs in a 9×13 inch baking dish.
Bake meatballs in the preheated oven for 20 minutes. Pour the spaghetti sauce into a large saucepan; bring to a simmer over low heat. Stir baked meatballs into the simmering sauce. Do not turn oven off. Simmer sauce until meatballs are fully cooked, about 20 minutes.
Place one meatball, a sprinkle of mozzarella, a sprinkle of Parmesan, and a bit of sauce between each roll. Place sandwiches in hot oven; bake until cheeses melt, about 7 minutes.
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