In a large bowl, combine the rice flour, potato starch, sorghum flour, xanthan gum, baking powder, baking soda, sugar and salt and stir to combine. Cut in the cold butter with a knife. Add the buttermilk and mix with a spoon until well combined.
Wrap the dough in a plastic wrap and place in the refrigerator for 60 minutes. While dough is chilling, preheat the oven to 450 degrees and line a baking sheet with a parchment paper.
Remove the dough from the refrigerator and between the sheets of plastic, roll out the dough to a thickness of about an inch to an inch and a half, depending on how large you'd like your biscuits. Peel back the top layer of plastic and cut out rounds of dough using a floured biscuit cutter .
Place dough on the prepared baking sheet. Re-roll any leftover dough and again cut out rounds of dough.
Use your hands to shape any small, left-over dough.
Place the baking sheet in the preheated oven and bake for approximately 20 minutes, until the biscuits are golden.