Mix spice rub ingredients; rub over pork. Transfer to a 6-qt. slow cooker. In a small bowl, mix water and beef granules; pour around roast. Cook, covered, on low until meat is tender, 6-8 hours., Remove roast; cool slightly. Reserve 1/2 cup cooking juices; discard remaining juices. Shred pork with 2 forks. Return pork and reserved juices to slow cooker; heat through. , Spoon a scant 1/3 cup shredded pork across center of each tortilla; top with a scant 1/3 cup each beans and rice. Fold bottom and sides of tortilla over filling and roll up. If desired, serve with toppings. Freeze option: Cool filling ingredients before making burritos. Individually wrap burritos in paper towels and foil; freeze in a freezer container. To use, remove foil; place paper towel-wrapped burrito on a microwave-safe plate. Microwave on high until heated through, turning once, 3-4 minutes. Let stand 20 seconds. If desired, serve with toppings., ,