Rooftop Farm On top of Coop

We are about to begin designing a rooftop garden for a Coop which will sell fresh Organic Produce in Rome, Italy. I have built a hundred or so mortise and tenon raised beds for terraces and several rooftops in Los Angeles and NY but was thinking I'd like to do some Hugelkutur beds for this rooftop because I'd like to take advantage of the flash flooding and protect produce from high winds. Does anyone have any thoughts on this? The building itself has not gone up yet so what do you think? Has anyone done rooftop and do you have any insights you'd like to share. Thanks very much.

Be careful with loading, a hugel is a sponge so it can hold a LOT of water. You could put the hugels above any load bearing walls to help, but still it can be a large load.

What R. Scott said.