Preheat oven to 375°F.
Grease a 10x15-inch jelly roll pan, line it with parchment paper, and grease the parchment.
Beat the eggs on high for 2 to 3 minutes.
Gradually add the granulated sugar, pumpkin, and lemon juice.
In a separate bowl, combine the flour, baking powder, cinnamon, ginger, nutmeg, and salt.
Stir the dry ingredients into the wet ingredients and mix well.
Spread the batter evenly into the prepared pan. Top with chopped walnuts, if using.
Bake for 15 minutes, until a toothpick inserted in the center comes out clean.
While the cake is still hot, lift it out of the pan by the parchment and sprinkle the top generously with powdered sugar.
Starting at a short end, roll the hot cake up tightly in the parchment. Let it cool completely.
While the cake cools, beat the powdered sugar, cream cheese, butter, and vanilla until smooth.
Gently unroll the cooled cake and spread the filling evenly across it.
Roll the cake back up, peeling the parchment away as you go.
Place seam-side down on a serving plate, dust with more powdered sugar, slice, and serve.