1. Preheat grill to medium-high heat.
2. Bake rolls according to package directions. Split rolls.
3. Remove casings from sausage. Combine sausage, chopped basil, and next 5 ingredients (through ground sirloin) in a medium bowl. Divide beef mixture into 6 equal portions with moist hands, shaping each into a 1/2-inch-thick patty. Press thumb in center of each patty, leaving a nickel-sized indentation.
4. Place patties on grill rack coated with cooking spray; grill 6 minutes. Turn patties over; grill 2 minutes. Sprinkle cheese evenly over patties, and grill 6 minutes or until a thermometer registers 160°. Remove from grill; let stand 5 minutes.
5. Place 1 basil leaf on bottom half of each roll; top each with 1 patty, 1 tablespoon marinara sauce, and roll top.