Place vegetables in bottom of large slow cooker, arranging potatoes on top. Add water to slow cooker. Sprinkle garlic over vegetables.
Season roast on all sides with Beef Rub. Place roast on top of vegetables in slow cooker. (Sprinkle with any remaining Rub.)
Pour Marinade and soy sauce over the roast. Cover.
Cook 7 to 8 hours on LOW, or until the vegetables and meat are tender. Skim fat, if needed. Serve in shallow bowls with crusty bread for sopping up the juices, if desired.