In a large skillet, cook the sausage, onion and pepper over medium heat until sausage is no longer pink; drain. Transfer to a 4-qt. slow cooker. Add the meatballs, tomato sauce, tomatoes, tomato paste, Parmesan cheese blend, garlic and seasonings. Cover and cook on low for 4-5 hours or until hot and bubbly.
Sprinkle with mozzarella cheese. Cook 15 minutes longer or until cheese is melted. Serve with pasta.