Grease a 15x10x1 or 46 cm jelly roll pan. Line with waxed paper. Grease and flour the waxed paper.
Sift together flour, baking powder, cinnamon, pumpkin pie spice, nutmeg, and salt; set aside. Beat eggs and sugar until thick and fluffy, beat in pumpkin and lemon juice. Stir in dry ingredients all at once. Pour into prepared pan, spreading evenly with spatula. Sprinkle with nuts (or mix into filling).
Bake for 15 minutes at 350 or until center springs back when lightly touched. Loosen cake around edges with a knife. Invert onto clean damp towel dusted with confectioners sugar; peel off waxed paper. Trim 1 cm from all sides. Roll up cake and towel together from short side. Place seam side down on wire rack, cool completely.
Unroll cake. Beat last 4 ingredients until smooth. Spread on cake. Reroll cake. Refrigerate.