initially i used to belive that water makes roti soft , but as i read more and do more experiment i realized mixture of water and oil ( emulsion ) makes roti soft , that is because where as water makes roti soft , oil trap that water inside roti because roti has to go through heat and cool cycle so that will evaporate water inside it , same happens when you microwave roti without sealing inside a air tight container , it makes roti as hard as rock , so moral of the story ? use wise mixture of water and oil to make roti , also cover the roti in oil coating by putting more oil when you store it ( inside or outside refridgerator ) , to that end whenever roti need to be heat in microwave do so in airtight container and put some water drops inside container to produce steam, also using milk to make roti will be the best instead of oil this is because milk is natural emulsion , obviously quality of dough makes difference too , however key players are same
Interesting theory! I never add oil or Milk to my chapatti dough and my chapatties are always soft. I have never seen any north Indian, the main chapatti eaters of India, adding oil to chapatti dough. To paratha and pooro dough yes, but to chapatti dough, no.
I know that in some regions of India they do add oil, but it is not the norm.
The trick is to make the dough soft, cook on a hot (not over hot) gridle, put them in a stack and keep them in an airtight container or wrapped in aluminium foil.
Hope this helps😀