Grease and flour a 15x10x1-inch jelly-roll pan; set the pan aside. In a small bowl, stir together the flour, baking powder, and ground cinnamon.
In a medium mixing bowl, beat egg yolks with an electric mixer on high speed for 5 minutes or until thick and lemon-colored. Gradually add the first 1/2 cup granulated sugar, beating on high speed until sugar is almost dissolved. Add pumpkin and beat on low speed until just combined.
Thoroughly wash the beaters. In a large mixing bowl, beat egg whites on medium speed until soft peaks form (tips curl). Gradually add the second 1/2 cup granulated sugar, beating until stiff peaks form (tips stand straight).
Fold egg yolk mixture into beaten egg whites. Sprinkle flour mixture over egg mixture; fold in gently by hand until just combined. Spread batter evenly in the prepared pan.
Bake in a 375 degree F oven for 12 to 15 minutes or until cake springs back when you touch it lightly. Immediately loosen edges of the cake from pan and turn the cake out onto a towel sprinkled with powdered sugar.
Starting from a short side, roll up the warm cake and powdered-sugar-coated towel together. Let cake cool to room temperature on a wire rack, about 1-1/2 to 2 hours.
Meanwhile, for filling, in a medium mixing bowl, beat the cream cheese, butter, and vanilla with electric mixer until combined. Add the 1 cup powdered sugar; beat well.
Unroll cake; remove towel. Spread cake with filling to within 1/2 inch of edges. Roll up cake. Wrap in foil or plastic wrap. Chill the mixture for at least 2 hours.
To serve, sprinkle the cake roll with additional powdered sugar. Cut cake into slices. Place the slices on dessert plates. Garnish with frosted grapes and top with whipped cream, if you like. Makes 10 servings.