Preheat oven to 400°F (200°C).
In a large mixing bowl, combine ground meat, breadcrumbs, egg, onion, garlic, Italian seasoning, salt, and pepper.
Mix until just combined (do not overmix).
Roll into 1–1.5 inch meatballs and place on a parchment-lined baking sheet.
Bake for 18–20 minutes, or until browned and cooked through.
Alternatively, pan-fry in a skillet over medium heat, turning to brown all sides.
In a large saucepan, bring marinara sauce to a simmer.
Add cooked meatballs and simmer for 10–15 minutes to let flavors meld.
Split rolls open without cutting all the way through.
(Optional) Brush with butter and toast in the oven for 3–5 minutes until lightly crisp.
Spoon meatballs and sauce into each roll.
Top with mozzarella and provolone cheese.
Place under the broiler for 2–3 minutes, until cheese is melted and bubbly.
Sprinkle with parmesan and fresh herbs if desired.
Serve immediately with your favorite sides.
