In 2-cup microwavable measuring cup or small microwavable bowl, mix water and cornstarch until smooth. Pour juices from cooker into cornstarch mixture; mix well. Microwave on High 1 to 2 minutes, stirring once halfway through cooking, until mixture boils and thickens slightly. To serve, spoon turkey onto bottom halves of rolls; spoon sauce over turkey. Cover with top halves of rolls.