Fujii, there has never been a rooftop helipad in Oz, and probably never will, other than those for hospitals, and they are generally on top of the carpark.
The public has rejected piloted helicopters in populated areas, and has never allowed a CBD heliport in Sydney, except for a brief period on a wharf in Darling Harbour. Many a council now has a specific policy prohibiting helicopter landings in their areas.
Look at a rooftop, it is covered with mobile phone antennas, aircon units, flagpoles. The greatest rooftop helipad was Pan Am, and after the disaster when a chopper rolled over and killed people on the rooftop and a piece fell into the street and killed a pedestrian, it was shut down.
Who is going to supervise an arrival/departure? No building owner will permit Joe Blow to wait on the rooftop for his Uuuuber chopper without somebody to cover their backsides for liability. In fact, nobody is allowed on ANY rooftop without massive OHS precautions, coveralls, tie-downs, fences around the edges etc.
This jetson-like dream of zipping through the city streets like in 5th Element, landing on rooftops and over train stations has no chance of working in our NIMBY society.