Sausage Meatball Sandwiches

Name: Sausage Meatball Sandwiches
Ingredients: 1 1/2 pounds hot and/or sweet Italian sausage, casings removed; 8 tablespoons olive oil, divided; 1 fennel bulb, core removed, thinly sliced; 1 large onion, chopped; 10 cloves garlic, thinly sliced, divided; Kosher salt, freshly ground pepper; 1 28-ounce can whole peeled tomatoes; 1 cup (packed) basil leaves; 4 soft hoagie rolls, split lengthwise down tops; 4 ounces fresh mozzarella, sliced