Cook pasta according to package directions to al dente; drain and rinse in cold water.
In a large skillet, cook the beef, onion, and green pepper over medium heat until meat is no longer pink; drain.
In a large bowl, combine the ricotta cheese, 1 cup cheddar cheese, egg and half of the beef mixture.
In a small bowl, combine the tomatoes and Manwich Sloppy Joe Sauce. Spread ¾ cup of the sauce mixture into a 13-in x 9-in baking dish coated with cooking spray.
Spoon cheese mixture into pasta shells; place in baking dish.
Combine remaining beef mixture and sauce; spoon over shells. Sprinkle with remaining cheese.
Cover and bake at 350 degrees for 40 minutes. Uncover; bake 5-10 minutes longer or until cheese is melted.
Note: This meal can be prepared in advance and kept in the refrigerator overnight. When ready to bake, remove from the refrigerator and allow to sit on counter for 30 minutes before baking (covered).