Spread the burrito shell out. Layer the rice, sweet potatoes, black beans, and chicken a little right of center, leaving an inch on the bottom and the top. Cover with cheese. Fold the bottom part of the shell up and top part down, then roll the burrito from right to left. Repeat with remaining shells and fillings. Wrap in saran wrap then place in a zip lock freezer bag for storage. To reheat, remove from saran wrap, wrap in a damp paper towel, and microwave the burrito for 1 minute. Flip over, and microwave an additional minute, if needed. Place in the toaster oven for a few minutes, if desired. Serve with sour cream, salsa, guacamole, or hot sauce.