I agree with Marc’s reply. You really do need to seriously consider your species selection well, and what function those species are required for ie. filtration of pollutants or filtration for reduction of roof run-off and stormwater flow reduction etc.
Endemic species in relation to your site is perhaps your first area of research…then consider the exposure to climatic changes due a roof setting – no shelter or minimal shelter from other structures.
Good luck with your green roof development!
