Whether the charcoal (kayu arang) enhances the roti canai in either aroma or taste is debatable.

I for one, couldn’t detect any enhancements. It could be that our orders were roti tampal (eggs + roti canai) and Roti Nachos (a pizza with roti canai as base) and since both were not plain roti, the presumably added smoky flavours were lost on us.