In a stainless steel pot, add in all the ingredients for the rice roux. Whisk well and cook this on medium heat until it bubbles. Whisk while cooking so the bottom of the pan doesn't burn. Once it has bubble, continue whisking for 30 secs and then remove it from the heat. Allow this to cool for at least 30 minutes at room temp (stirring occasionally to cool/release steam) before adding it to the dry mixture. If you pour this hot roux in immediately to the dry ingredients, it will cook the starches and create a thick batter (which will be harder to press) so just let the roux sit (uncovered) on the counter for 30 minutes to chill before adding it in. Just make sure to come once in a while to stir it. We just don't want to work with a extremely boiling off the heat roux.
For the dry mixture
In a KitchenAid mixing bowl or a good size stainless steel bowl, add in the rice flour, tapioca starch, and xanthan gum. Mix well and add in the rice roux.
Place it in the KitchenAid mixer with a whisk attachment and turn on to level 1 and mix for about 30 secs. Gradually bump up the speed to mix the batter until it has become completely smooth. I mixed it for about 3 minutes. You can also use a hand mixer if you don't have a KitchenAid mixer. Once it's well mix, finish with a spatula to make sure the dough is all evenly mixed. Cover with plastic wrap touching the dough so it doesn't dry out if you're not going to use it right away.
Cooking the noodles
In a big wide pot, add in water about 2/3 to 3/4 full. Bring to a boil and then reduce the heat to medium low. You don't want the water to be boiling while pressing the noodles in because the bubbles can break the noodles. Just keep it on a good gentle simmer. Place the rice batter into a noodles press or a potato ricer about 3/4 full. Swirl the water in the pot with a chopstick and then firmly press the batter into the water. Turn the heat up to high and gently separate the noodles with a chopstick when it floats to the top and just let it cook for about 1 minute. The noodles floating to the top means they're pretty much cooked. Remove the noodles with a spider and place into a bowl of cold water. Rinse well with cold water gently (at least 2x) and with your fingers, individually portion the noodles and place it into a colander to drain out any excess water.
Repeat until all the batter is used up. Just make sure the batter is always covered in plastic wrap so it doesn't dry out.
Allow the noodles to drain well and then you're ready to enjoy. I like to eat them the day they're made. It's textually better since it still has a good chew to it. If you have leftover, cover well with plastic wrap and place in the fridge if needed. I left my leftover in the fridge overnight and it still stayed pretty tender (although it can harden the longer it sits). Rewarm in the microwave if needed to loosen them. HOWEVER, the noodles will get too soft or break apart the more it sits. So best to use the day they're made.
Notes
I highly recommend measuring out the ingredients with a kitchen digital scale to get consistent flour measurements. Your dough will also be more consistent in texture.