Preheat the oven to 350F degrees.
In a medium skillet, crumble and brown the ground beef over medium heat until completely browned. Drain off the excess fat.
Reserve ¾ cup of the spaghetti sauce; set aside. Add the remaining spaghetti sauce to the skillet with the ground beef. Stir well then cover and simmer over medium-low heat for 10 minutes, stirring occasionally.
Spread ¼ cup of the reserved spaghetti sauce into the bottom of a 9x13 inch glass baking dish. Arrange one third of the frozen ravioli in a single layer in the pan.
Top the ravioli in the pan with half of the ground beef mixture, then sprinkle with 1/3 cup of the shredded mozzarella cheese.
Place another 1/3 of the frozen ravioli in a single layer over the meat sauce and cheese. Top with the rest of the meat sauce and another 1/3 cup of the shredded mozzarella cheese.
Place the final 1/3 of the frozen ravioli on top of the casserole. Top with the remaining ½ cup of the spaghetti sauce. Sprinkle with the remaining 2/3 cup of shredded mozzarella cheese.
Bake the casserole at 350F for 30-40 minutes, until the cheese is completely melted and beginning to bubble around the edges.