Preheat oven to 375°F (190°C).
In a large bowl, combine ground beef, bread crumbs, Parmesan cheese, garlic powder, onion powder, Italian seasoning, salt, and pepper. Mix well.
Form mixture into 16 meatballs.
Grease a baking sheet with olive oil. Arrange meatballs on the baking sheet.
Bake for 10-12 minutes, or until cooked through.
While meatballs are baking, cut sub rolls in half lengthwise.
Place 4 meatballs on each bottom half of the roll.
Top each with marinara sauce and mozzarella cheese.
Bake for an additional 5-7 minutes, or until cheese is melted and bubbly.