To make sauce, drain raspberries, reserving syrup. Add water to syrup to make 3/4 cup. In 1-quart saucepan, mix syrup mixture and cornstarch. Add jelly; cook and stir over medium heat until thickened and clear. Stir in raspberries. Refrigerate until cold. Serve cheesecake with sauce. Cover and refrigerate any remaining cheesecake and sauce.