A meatball sub is typically made of a long roll or baguette that is filled with cooked meatballs, sauce, and cheese. The meatballs are usually made with a mixture of ground beef or pork, breadcrumbs, and various seasonings, and are formed into balls and cooked either by frying or baking. The sauce used for the sub is usually a tomato-based sauce, like marinara or spaghetti sauce, that is seasoned with herbs and spices.