Preheat the oven to 400F. Line 2 baking sheets with parchment paper.
In a large bowl, combine gluten-free flour, xanthan gum (if using), baking powder, baking soda, granulated sugar, garlic powder, salt, black pepper, and fresh rosemary. Stir until combined.
Add the cubes of cold butter to the flour mixture and work with your hands or a pastry cutter until the butter is worked in to the flour and size of small peas. It's okay if you have some larger pieces in there.
Stir in the shredded cheddar cheese.
Starting with 3/4 cup, add in the milk until the mixture just reaches a paste-like consistency. I used a little less than 1 cup of milk to reach this point.
Spoon or scoop 1/4 cup of dough onto the prepared baking sheets, leaving at least 2 inches between each dollop of dough (there should be 12 total dollops of dough).
Bake the biscuits at 400F for 18 to 22 minutes, until the biscuits are a light golden brown. Serve warm.