Preheat the oven to 375 degrees F. Line a 10x15-inch jelly roll pan with parchment paper.
In a large bowl, whisk together the millet flour, rice flour, tapioca starch, pumpkin pie spice, baking powder, baking soda, xanthan gum, and salt.
In a separate bowl, whisk together the pumpkin puree, sugars, eggs, and vanilla.
Pour the wet ingredients into the dry ingredients, and stir until thoroughly combined. Pour the batter into the prepared baking sheet, and spread out until you have an even layer.
Bake in the preheated oven for 13-15 minutes, or until the cake bounces back when gently pressed.
Remove from oven and, using a sifter, immediately sift the additional confectioners' sugar over the cake, until the entire cake is covered. This will help to prevent the cake from sticking when you roll it up.
Place a lint-free, thin kitchen towel over the cake, making sure that the cake is covered, and one edge lines up with the 10-inch side of the cake. Place a cooling rack on top of the cloth, and carefully flip the baking pan upside down, turning the cake onto the cooling rack.
Carefully remove the parchment paper from the bottom of the cake and, starting on the 10-inch side, roll the cake into a log. Be sure to roll the cloth along with the cake, that will ensure that you can unroll it later to put the filling in. Allow the cake to cool for about 1 hour.
Beat together the softened cream cheese and butter until smooth. Add the confectioners' sugar and vanilla. Beat until smooth again.
Unroll the pumpkin cake, and spread the cream cheese filling over the cake, leaving 1-inch clear at the 10-inch side that will be the outside of the roll.
Roll up the cake again, this time without the cloth. I like to roll the cake up in the lint-free towel again, just to help hold it's shape. Wrap in plastic wrap, and refrigerate for at least 4 hours before serving. The Pumpkin Roll Cake can be made one or two days in advance.
Remove from the refrigerator 30 minutes before serving to allow the filling to soften slightly. Slice into 1-inch slices and serve.
Recipe by Faithfully Gluten Free at http://www.faithfullyglutenfree.com/2013/11/gluten-free-pumpkin-roll-cake.html