Grease and flour a 15x10x1-inch baking pan. In a bowl stir together flour, cocoa powder, baking powder, and salt. Set aside. In a small mixing bowl beat egg yolks and vanilla with an electric mixer on high speed about 5 minutes or until lemon-colored. Gradually add the 1/3 cup granulated sugar, beating on medium speed 5 minutes or until sugar is almost dissolved. Wash beaters.
In a large mixing bowl beat egg whites on medium speed until soft peaks form (tips curl). Gradually add the 1/2 cup granulated sugar, beating on high speed until stiff peaks form (tips stand straight). Fold egg yolk mixture into beaten egg whites. Sprinkle flour mixture over egg mixture; fold in gently just until combined. Spread batter evenly into prepared pan.
Bake cake in a 375 degree F oven for 12 to 15 minutes or until top springs back when lightly touched. Immediately loosen edges of cake from pan; turn out onto a towel sprinkled with powdered sugar. Roll up towel and cake, starting from one of the short sides. Cool on a wire rack.
Unroll cake. Spread softened ice cream on cake to within 1 inch of edges. Roll up cake without towel. Wrap in foil; freeze 4 hours or up to one week.
In a blender container or food processor bowl cover and blend or process thawed raspberries on high speed until smooth. Press through a strainer to remove seeds; discard seeds. In a small saucepan stir together the raspberry puree, the 3/4 cup sugar, and the lemon juice. Bring mixture to boiling over medium-low heat. Boil for 3 minutes, stirring constantly. Transfer sauce to a bowl.
To serve, slice ice cream roll; place slices on dessert plates. Spoon sauce next to each slice. If desired, decorated sauce using melted white chocolate and garnish with raspberries. Makes 10 servings.