1) Preheat oven 350 degrees. Line a 10X15 inch jelly roll pan with parchmentpaper, and greasepaper. Set Aside.
2) In a large bowl, beat eggs with an electric mixer until lemon colored. Gradually add sugar. Stir in pumpkin and lemon juice. In a separate bowl, sift together flour, baking powder, cinnamon, ginger, nutmeg, and salt; foldinto egg-pumpkin mixture. Pour batter into prepared pan, smooth out top, and sprinkle with chopped nuts. Bake for 15 min.
3) Lay a clean kitchen towel out on the counter. Sprinkle powdered sugar on kitchen towel. Turn the warm cake onto towel and remove parchment paper. Roll up cake and towel lengthwise. Cool in refrigerator or freezer.
4) While cake cools, beat margarine and cream cheese together until smooth. Beat in 1 cup powdered sugar. Add vanilla. Unroll cake roll in half. Wrap each roll in plastic wrap until served. Store in refrigerator, or freeze for later use. Cut rolls in 1-inch slices to serve.