Preheat oven to 180 C / Gas 4. Grease and flour a 25x38cm or similar sized Swiss roll tin.
In a large bowl, beat eggs and sugar with an electric mixer on high speed for five minutes. Gradually mix in pumpkin puree and lemon juice. Combine the flour, baking powder, salt, cinnamon and ginger; stir into the pumpkin mixture. Spread batter evenly into the prepared tin. Sprinkle pecans over the top of the batter.
Bake for 12 to 15 minutes or until the center springs back when touched. Loosen edges with a knife. Turn out on two tea towels that have been dusted with icing sugar. Roll up cake using towels and let cool for about 20 minutes.
In a medium bowl, combine cream cheese, butter, 120g icing sugar and vanilla. Beat until smooth. Unroll pumpkin cake when cool, spread with filling and roll up. Place pumpkin roll on a long sheet of greaseproof paper and dust with icing sugar. Wrap cake in greaseproof paper and twist ends like a sweet wrapper. Refrigerate overnight. Serve chilled; before slicing, dust with additional icing sugar.
For the pumpkin, you can steam, boil or bake it. Mash well or puree in a blender, then allow to cool thoroughly before adding to the cake mixture. Alternatively, you can use tinned or jarred pumpkin puree, if available.