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.