Add all the meatball ingredients into a mixing bowl and mix until combined. Using your hands, shape the mixture into 1-inch balls and place them on a plate.
Add some oil to a non-stick pan and place it over medium heat. Once hot, add the meatballs and cook for 5-6 minutes, flipping halfway through. Remove the meatballs onto a plate.
Place the pan back over medium heat then add the olive oil, onion, and garlic. Cook until fragrant, then add the rest of the sauce ingredients and bring to a simmer. Once simmering, add the meatballs back and cook through.
Preheat the oven to 200C/400F.
Slice your hoagie rolls in half and add a generous portion of the warm meatballs. Add the marinara sauce on top, followed by the mozzarella cheese.
Place the filled hoagie rolls open faced on a baking sheet and broil for 2-3 minutes, until the cheese begins to melt.
Remove from the oven and serve immediately.
