Preheat the oven to 400?F (200?C).

In a mixing bowl, combine ground beef, bread crumbs, egg, garlic powder, onion powder, salt, pepper, parmesan cheese, and parsley. Mix until well combined.

Form the mixture into meatballs, about 1 inch in diameter.

Place meatballs on a baking sheet and bake for 20 minutes or until cooked through.

In a skillet, heat marinara sauce over medium heat. Add the cooked meatballs to the sauce and simmer for 5 minutes.

Slice the sub rolls lengthwise and place them on a baking sheet.

Spoon the meatballs and sauce into each roll, then top with shredded mozzarella cheese.

Broil in the oven for 2-3 minutes until the cheese is melted and bubbly.