Begin by preparing the meatballs as per the package instructions, or if you prefer homemade, mix all the meatball ingredients together. Shape the mixture into 1-inch balls and place them on a parchment-lined baking sheet. Bake at 350°F for about 20 minutes or until they are fully cooked.
Once the meatballs are ready, transfer them to a saucepan containing the pasta sauce. Let them simmer on low heat for 10 minutes with the lid on.
In the meantime, spread garlic butter inside each hoagie roll. Set your broiler to heat and toast the rolls until they turn a golden brown, which should take roughly 3 minutes.
Arrange the toasted rolls in a 9x13-inch baking dish. Fill each roll with four meatballs, topping them with a bit of sauce and shredded cheese.
Broil the assembled subs for 2-3 minutes, or until the cheese is thoroughly melted. Serve with additional sauce on the side for dipping, if desired.