Los Angeles used to have a Fire Safety Code that required flat roofs and often times....helidecks on tops of buildings.
Yes fire, flames, heat, smoke, and debris in the air can prevent rescues.
But....in a lot of cases rescues could be made by Helicopter.
In Los Angeles, with the size of the Police and Fire Departments helicopter fleets and other helicopters it was a very viable concept.
They are beginning to re-think the flat roof concept.
If there is no infrastructure built into the Building Roof Top.....then for sure the probability of a successful rescue are reduced.
In high rise buildings....sometimes going down is not an option and jumping would be fatal....thus that means the only other Option might be to go up to the roof and pray Rescue Helicopters can get to you.