In a large bowl combine 1/2 of the mozzarella cheese, cottage cheese, spinach, Parmesan cheese, egg, oregano and garlic; stuff into uncooked cannelloni. Place in a lightly oiled or buttered 22x33cm baking dish.
Add sausage into a large frying pan then cook over medium heat until no longer pink. Drain fat. Stir in pasta sauce until hot then pour over cannelloni. Pour water along sides of baking dish.
Cover and bake at 180 degrees C for 1 hour. Uncover; sprinkle with remaining mozzarella. Bake 5-8 minutes longer or until cheese is melted. Let stand for 10 minutes before serving.