Preheat the oven to 350°F. Line an 8x8" glass baking dish with parchment paper.
In a large mixing bowl, combine all of the meatball ingredients. Thoroughly mix the ingredients together using your hands.
Use a cookie scoop to scoop up some of the meat and roll it into a ball between your hands. Place the meatball in the baking dish. The meatballs can be placed fairly close together on the parchment paper, just not touching. You should be able to make 15-16 meatballs.
Bake the meatballs for 25-30 minutes or until the internal temperature reads 160°F. Remove the meatballs from the oven and increase the oven temperature to 400°F.
Line a glass baking pan with parchment paper, the pan should be able to snuggly fit the number of subs sandwiches you are making. Prep the sub rolls by cutting each roll open and buttering inside if desired (you can skip this step to keep the meal dairy-free).
Place 3-4 meatballs in each sub roll. Add plenty of pasta sauce to each sub. Place the subs side-by-side in the glass baking dish. Liberally sprinkle the mozzarella cheese over the subs. Top the subs with a sprinkle of parmesan cheese.
Cover the pan with aluminum foil and bake the subs for 10-15 minutes or until the cheese has melted. Enjoy warm!