Place the flours and salt in a bowl, making a "well" in the centre. Pour in the water and mix until a soft dough forms.
Gentley knead the dough on a hard surface that has been lightly dusted with additional amaranth flour. Knead for 3 minutes or until smooth. Divide the mixture into 8 equal portions. Roll out each portion into a circle.
Using a non-stick frypan, cook over a medium heat until cooked and golden on both sides. Cook one at a time.
Lightly brush with meted butter and keep warm while you cook the remaining roti.