Preheat grill. Season chicken breasts with chicken seasoning. Grill over medium heat for 5 to 8 minutes on each side or until fully internal temperature reaches 165 degrees F.
Top chicken with sliced cheese keep on grill until cheese melts; remove from grill and keep warm. Brush cut sides of rolls lightly with oil; grill for 1 minute.
Toss lettuce blend and tomatoes with vinaigrette in a medium bowl. Spread mayonnaise equally on cut sides of sandwich rolls. Layer lettuce blend, grilled chicken breast and avocado slices (optional) on each roll. Serve sandwiches immediately.