I have slept on the roof top just few times, Hamarey ghar main tu AC hota tha , wo laga ke sotey they 
Waisay experience is not that bad, at night it is pleasent looking at stars.
Waisay just an experiment we did when we were kids… if we look at clear sky at night we are able to see lots of tiny stars. but if we see it through binoculars, we see hardly any stars. Or if we place a mirror and try to see the reflections of these stars then we wont be able to see any of them 
This is because our eyes have so strong lenses that they capture light from great distance, which other ordinary equiptments ( binoculars, camera) fail to capture 