Crumble the ground beef and Italian sausage into a large skillet. Cook over medium-high heat until browned. Drain.
Combine the ground meats, marinara sauce, mushrooms, and tomatoes in a slow cooker. Cover, and cook on LOW heat for 7 to 8 hours.
Stir in the tortellini, and sprinkle the mozzarella and cheddar cheese over the top. Cover and cook for 15 more minutes on LOW, or until the tortellini is tender.
