This is the company I've seen most:
American Hydrotech, Inc. - Garden Roof Assembly (Green Roof), Ultimate Assembly, Waterproofing and Roofing
Not their "Garden Roof" but this other system:
MM6125® - Roofing Application
It is installed below pedestal paver deck systems used on high-rise buildings, such as elevated walkways, roof pool deck areas, and the like.
Most warranties by most roofing companies of any type only warranty their "material", no labor and no overburden. That means if you have a leak, they will be pleased (more than happy to) drop off a roll of material and some hot mop material so you can pay someone to: remove the overburden (the pavers, the pedestal paver support system, the material which is leaking, patch the material which is leaking, then pay someone to put all the other material back), American Hydrotech's warranty covers all costs involved in making the repair, not just 'here is some patching material, go for it'.
It takes a lot of confidence in your product to offer a warranty which puts you at risk of having to pay for removing and replacing all of the overburden, which is multiple times more expensive than the cost of the actual repair.
Not saying their product is the best, or that their installers are the best (each one I've inspected was 'not being done correctly'), but that they have a factory representative who does installation visits and signs off on the installation, by installers trained in installing their product. That said, it is amazing how poorly those installers remember what they are supposed to do.
In one case, the material was heated too hot, so, after a big brouhaha about it, and with everyone on deck looking at what they were doing, where I was pointing out other 'not correct' work as they were doing the work (you would think the installers would do it right with everyone watching), everyone checked the temperature of the material and said it was okay, so I checked the gage and the temperature was too low - meaning everyone else went back and looked at the temperature gage again, and, yes, the temperature was too low (not by much, still, though, it was "not hot enough").
When you have specially trained installers, the factory representative, all the contractors representatives, along with the owner's representatives on the roof standing there watching it being applied ... and the installer STILL does it wrong, that is ... unbelievable.
