Preheat oven to 375°. Line a baking sheet with parchment paper and set aside.
In a medium bowl, stir together the panko, parsley, egg, oil, ketchup, cheese, onion powder, garlic, salt and pepper. Add the ground beef and gently stir to combine. Roll the meat into 12 meatballs.
Arrange the meatballs on the prepared baking sheet and bake until cooked through, about 15 minutes. Cool for 10 minutes.
Slice a meatball in half and arrange 2 meatball halves on the bottom half of a roll. Top with top half of roll. Repeat with remaining meatballs and rolls.
Serve immediately with additional ketchup, if desired.