I like the idea of green roofs and believe they will improve quality of life in Denver so would like to see them encouraged.  However, I think they be oversold and would like to see the data that support the claims presented in an easily accessible way.  For example, the greenroof sight gives data from the Botanic gardens which show that the roofs will require water and will return less water to the river. It would be useful to have an estimate on how large that amount would be if the initiative passes. Certainly there is polluted runoff from a city but how much of that is from roofs vs the oil, antifreeze, tire wear, etc. from streets and parking lots.
I would like to see a comparison of green roof vs PV with improved insulation on a net energy basis.  Such data from a Denver climate would help with an informed decision.