I was under the impression that roti are a form of laminated dough - where there the flour and water are stretched very thinly, then margarine applied , then rolled into a snake, then coiled into a disk. This disk is then fried on a flat top (in ghee or margarine) or sometimes grilled... but any type of dough type thing that is that flaky always has lots of fat - that's how you get that flakiness - during cooking, the fat melts, and the water in the dough turns to steam separating into layers.
ETA: Sorry, after some research, I realized that I incorrectly assumed that the roti typical in Sri Lanka were the same as the roti prata found in Singapore - they looked similar from the pictures... but I now realize that they are very different, with totally different ingredients and methods...
