Spray a baking sheet with cooking spray. Preheat oven to 400 degrees F.
Place your frozen cooked meatballs or homemade cooked meatballs in a large pot. Cover with your pasta sauce. Gently fold the meatballs with the sauce, Heat the meatballs and sauce on low-medium, stirring occasionally, until the meatballs are heated thoroughly.
Fill a roll with as many meatballs as you can fit (usually 4-5 meatballs, depends on size of meatballs and the size of the roll). Top with more pasta sauce from your pot. Place filled sandwich rolls closely on baking sheet. Top each sandwich with shredded mozzarella cheese.