Coat a large skillet with cooking spray. Heat skillet over medium-high heat. Add chicken to hot skillet; cook until chicken is no longer pink, stirring to break apart. In a 3-1/2- or 4-quart slow cooker, combine chicken, pizza sauce, vegetables, and undrained tomatoes.
Cover and cook on low-heat setting for 6 to 8 hours or on high-heat setting for 3 to 4 hours.
Arrange split rolls, cut sides up, on an unheated broiler pan. Broil 3 to 4 inches from the heat for 1 to 2 minutes or until toasted. Spoon chicken mixture onto bottoms of toasted rolls. Top with cheese and roll tops. Makes 8 sandwiches.