Preheat oven to 400°F. Spray a sheet pan with olive oil, then arrange meatballs in a single layer. Bake for 15-20 minutes, until the internal temperature reaches 165°F when probed with a meat thermometer.
While the meatballs are in the oven, bring marinara sauce to a simmer in a wide sauté pan over medium-low heat. When meatballs are cooked through, add to sauté pan, and toss with sauce until thoroughly coated.
On a separate sheet pan, arrange rolls cut side up and place a slice of provolone in each roll. Bake for 5 minutes, until the bread is toasted, and the cheese has melted.
Fill each sandwich roll with 4 meatballs and a ladle of sauce to serve.