Combine ground beef, egg, bread crumbs and ¼ cup marinara sauce in a bowl and form into 1-inch balls.

Brown the meatballs in a lightly greased skillet. Once they’re browned, place the meatballs on a baking sheet and bake for 15 minutes at 375°.

Heat the remaining marinara sauce in a sauce pan.

Assemble the subs: place a slice of cheese on the bottom to the roll, add 4 meatballs and cover in marinara sauce.