I think this is very beneficial for multiple reasons.
1. It puts back the green space that was displaced when the building was built.
2. It will allow more animal species to thrive in the growing cities. Birds, and insects could thrive off roof top gardens.
3. With multiple gardens constructed, bridges/paths can be constructed to move from one area to the next. Each roof top could have a different theme, similar to the high line in New york.
4. Roof top gardens will help with island effect and micro-climates near the building and also with building run off.
Some issues to work though would be (all things I am still looking into)
1. placement of any mechanical equipment that is currently on the roof.
2. safety issues
3. how to make sure a garden with thrive properly.
Please list any other benefits or concerns so I can use them in my final project and make sure I have a clear argument!