If you have made extras, you can freeze some at this point before you put them in the red sauce. You can also serve them with a beef gravy or white sauce. Take any you want to make with red sauce and return them to the cooking pan. Don't clean the pan before doing so. Pour red sauce over the meatballs, and bring to a simmer as long as you have... the longer you can do that, the more they'll flavor the sauce.