In 10-inch skillet, cook beef and sausage over medium-high heat 5 to 7 minutes, stirring occasionally, until brown; drain.
Spray inside of 4- to 5-quart slow cooker with cooking spray. Mix beef mixture, marinara sauce, mushrooms and tomatoes in cooker.
Cover; cook on Low heat setting 7 to 8 hours.
Stir in tortellini; sprinkle with cheese. Cover; cook on Low heat setting about 15 minutes longer or until tortellini are tender.