Preheat oven to 350°F (175°C). Spray an 11 x 13-inch baking pan with cooking spray.
Cook the pasta shells, wheels, and spirals according to package directions until al dente; drain and set aside.
In a large skillet, brown the ground beef and the Italian sausage over medium heat until fully cooked; drain any excess fat.
Warm the spaghetti sauce in a saucepan or the skillet, then stir in the cooked ground beef and sausage until combined.
Layer the casserole: spread a portion of the meat sauce in the bottom of the prepared pan, add a layer of mixed cooked pasta, then sprinkle with some mozzarella and Parmesan, and top with some pepperoni, sliced onion, and sliced green pepper. Repeat to make about three layers, finishing with a generous cheese layer on top.
Bake in the preheated oven for about 45 minutes, or until the cheese is melted and bubbly and vegetables are tender.
Let the casserole rest a few minutes before slicing and serving.