To make puffed up soft phulkas even rolling and kneading good is the key.
The same can be done on the tava itself without open fire.
If you are going to make it and keep for long hours then smear it in ghee on both sides and roll it in a towel or a cotton cloth and keep it closed this way the chapatis will be soft.
Don't use more flour while rolling then while cooking the flour and your roti will burn and it may not puff up.
Smearing the rotis with ghee at last will prevent it from drying and it will also enhance the taste.
Don’t put too much pressure while rolling rotis make it with light hands you will get evenly rolled roti’s.
Adding oil while kneading the dough is optional.