Beat eggs on high speed for 5 minutes. Gradually beat sugar. Stir in pumpkin and lemon juice.
In a separate bowl, mix together flour, baking powder, cinnamon, ginger, nutmeg, and salt. Mix together and spread into a greased and floured 15x10x1 baking cookie sheet. Top with finely chopped walnuts.
Beat powdered sugar, cream cheese, margarine and vanilla until smooth. Spread over cake and roll back up and chill.
Bake at 375°F for approx. 15 minutes. Turn out on a towel (generously) sprinkled with powdered sugar. Starting at the narrow end, roll towel and cake together. Cool and then unroll.