In a large bowl, combine sausage and cottage cheese. Stuff into uncooked manicotti shells. Place in a greased 13x9-in. baking dish. Top with marinara sauce. , Cover and bake at 350° until a thermometer inserted into the center of a shell reads 160°, 55-60 minutes., Uncover; sprinkle with mozzarella cheese. Bake until cheese is melted, 8-10 minutes longer. Let stand for 5 minutes before serving. Freeze option: Transfer individual portions of cooled manicotti to freezer containers; freeze. To use, partially thaw in refrigerator overnight. Transfer to a microwave-safe dish and microwave on high, stirring occasionally; add a little spaghetti sauce if necessary.