Spritz the air fryer basket with nonstick spray and add the meatballs in a single layer.
Cook at 400 degrees for 10 minutes, shaking the basket gently halfway through cooking for even browning.
Add the meatballs to a bowl and top with the marinara. Stir to coat.
Slice open the hoagie rolls and spread the inside with butter. Sprinkle with the garlic powder and garlic salt.
Place the hoagie rolls in the air fryer, split open so the butter is facing up, and toast for 1-2 minutes at 400 degrees, until toasted to your liking.
Remove the rolls from the air fryer and divide the meatballs evenly between each roll. Spoon on extra sauce, as desired.
Sprinkle the tops of the meatballs with Parmesan cheese and arrange the sliced mozzarella over the top. Sprinkle with the parsley.
Roll the sandwiches tightly in foil and return to the air fryer.
Cook for 3 minutes at 400 degrees to warm everything together.
Serve hot.
Notes
If your marinara is room temperature, there is no need to warm it before adding it to the meatballs. If your marinara is cold from the fridge, you'll want to heat it a bit first.