In medium bowl, mix 1 can (15 oz) pumpkin pie mix (not plain pumpkin) and 1 egg yolk with whisk. Measure 1/2 cup powdered sugar; reserve 1 tablespoon of the powdered sugar, then stir remaining powdered sugar into pumpkin mixture. Spread mixture in thick layer all over pizza crust. Carefully roll up crust, starting with shorter edge. Try not to squeeze, or the pumpkin will ooze out.