Grease a 15- x 10- x 1-inch jellyroll pan with vegetable oil, and line bottom with waxed paper. Set aside.
Beat eggs in a large bowl until thick and lemon colored; gradually add sugar, beating constantly. Add vanilla; beat well.
Sift together flour, cocoa, soda, and salt. Sprinkle flour mixture over egg mixture, 1/4 cup at a time; carefully fold in after each addition.
Spread batter evenly in pan. Bake at 400° for 12 minutes or until cake springs back when lightly touched.
Sift powdered sugar in a 15- x 1 0 - inch rectangle on a linen towel. When cake is done, immediately loosen from sides of pan, and turn out onto sugar. Peel off waxed paper. Trim 1/2 inch off edges of cake. Starting at narrow end, roll up cake and towel together; cool on a wire rack, seam side down.
Unroll cake, and remove towel; spread cake with softened ice cream, and reroll. Place in freezer 3 hours or until firm.
Place cake on wire rack; pour Rich Chocolate Sauce over cake. Return to freezer 3 hours or until firm.
Place roll on a serving dish. Garnish with white chocolate leaves, if desired. Slice and serve on individual dishes.