In A Dutch Oven Coated With Nonstick Cooking Spray, Brown Roast On All Sides Over Medium-High Heat; Drain. Transfer To A 5-Qt. Slow Cooker. In A Bowl, Combine The Juice, Tomato Sauce, Onion, Vinegar, Salt, Ginger And Cinnamon; Pour Over Roast. Cover And Cook On High For 5-7 Hours. In A Small Bowl, Combine Cornstarch And Water Until Smooth; Stir Into Cooking Juices Until Well Combined. Cover And Cook 1 Hour Longer Or Until The Meat Is Tender And Gravy Begins To Thicken.