In 2-quart saucepan, stir orange juice, sugar, cornstarch and pepper flakes with wire whisk until cornstarch is completely dissolved. Heat to boiling over medium-high heat, stirring frequently. Boil 1 minute, stirring frequently. Remove from heat; stir in vinegar and orange peel. Cool completely, about 15 minutes.
Meanwhile, on center of each lettuce leaf, place equal amounts of bell pepper, cucumber and carrots; roll up, leaving ends open. Secure with toothpick; place on serving platter. Serve bundles with sauce.