Grate potatoes and add them to a bowl.Add buckwheat flour, chickpea flour, turmeric, cumin seeds and salt to the potatoes & mix them all very well.Now add warm water (1 Tbsp at a time) and mix until it reaches roti dough consistency. Add oil at the end and this should make the dough less sticky.Using rolling pin and a board, make rotis and throw them on a griddle, one at a time.Make rotis. They are super-soft.