Fry ground beef with a little oil. As beef is cooking, break it up in small pieces. Transfer beef to a large mixing bowl. Add salt, pepper, and garlic. Mix well. Add egg, cheese, parsley, bread crumbs, and more salt to taste. Squeeze water out of cooked spinach and chop.
Add spinach and 1⁄2 cup tomato sauce. Spread some tomato sauce on the bottom of a baking pan. Stuff cannelloni shells and place in pan. Spread more tomato sauce in between each layer and on the top. Bake at 350 degrees F for 1 hour. Then, broil for 2-3 minutes to brown top.