Place meatballs, carrots, onion. mushrooms, and meatballs in a crockpot. In a bowl, stir tomato sauce, beef broth, red wine. 3/4 cup water, and garlic powder. Pour over meatballs and vegetables.
Cover and cook on high for 4-5 hours.
One hour before it's to be done, thicken sauce with 2 tbsps. flour into 1/2 cup cold water.