Cheesy Italian Ravioli

1 lb. ground beef
15 oz. container marinara sauce (refrigerated is what I use)
(1 cup sliced mushrooms) - don't use this one because we're not big mushroom eaters
14 1/2 oz can diced tomatoes w/ italian seasoning, undrained
9 oz. package refrigerated cheese tortellini (or ravioli)
1 cup shredded mozarella cheese

Heat oven to 375. Brown the beef over medium heat. Drain off the fat. Add the marinara sauce, mushrooms, and tomatoes to the beef mixture and stir together. Pour half of this mixture into an ungreased 9x13 baking dish. Arrange the tortellini on top of the sauce and then cover with remaining sauce mixture. Top with shredded mozarella. Bake uncovered 20 to 25 minutes or until tortellini is tender and mixture is hot.