Untie rolled roast and trim fat. Reroll roast. Place meat in plastic bag. Set in shallow dish. Pour marinade into bag and close
Marinate in refrigerator 6 to 8 hours or overnight, turning bag several times.
Drain meat. Reserve 1 cup marinade. Place meat in a 325 oven about 2 hours or til meat thermometer reads 160. In a small pan, mix 1/4 cup water an cornstarch. Add marinade. Cook 1 or 2 minutes. Brush roast with marinade. Roast 1 hour more. Brush frequently.