In a large bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, parsley, garlic, egg, salt, pepper, oregano, and basil. Mix until well combined.
Form the mixture into meatballs, about 1.5 inches in diameter. You should have around 20 meatballs.
Heat a large skillet over medium heat and add a drizzle of olive oil. Brown the meatballs on all sides, about 5-7 minutes. They don’t need to be fully cooked through at this stage.
In a large baking dish, spread 1 cup of marinara sauce on the bottom. Place the browned meatballs on top and pour the remaining marinara sauce over them.
Cover the dish with aluminum foil and bake for 25 minutes. Remove the foil, place a slice of provolone cheese on each meatball, and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
While the meatballs are baking, lightly toast the hoagie rolls in the oven for about 5 minutes.
To assemble, place 3-4 meatballs in each hoagie roll, spoon extra sauce over the top, and serve immediately.