Make the Sauce: If making homemade sauce, follow instructions below. If using store bought, place the sauce in a pot over medium heat. Cover with a lid and bring to a low simmer.
Make the Meatballs: In a bowl, mix together the bread and milk. Let sit for 2 to 3 minutes. Mix in the ground beef, oregano, and parmesan, and season with salt and pepper. Mix until well combined. Using your hands, form the meat into equally-sized balls.
Heat a saute pan over medium heat. Add the oil, place the meatballs in batches without crowding the pan, and sear all around until nicely browned all over. Then place it into the pot of sauce. Cook the meatballs to an internal temperature of 160°F (71°C) using a thermometer. Season the sauce with salt and pepper to taste. Remove from the heat.
Preheat the oven broiler on low.
Prep the Roll: Drizzle the inside of the roll with oil. Place on a baking sheet. Lightly toast under the broiler.
Place the meatballs on the sub roll, spoon on some of the sauce, and then top with cheese. Place under the broiler until the cheese is melted and bubbly.
Combine sparkling water and lemon slices. Serve over ice if desired.
Cut the sandwich in half and serve with carrots and ranch and lemon sparkling water.