Thanks for featuring this on Newswire, Rockstar!
Full Disclosure: I'm a member of Nomad Union, the same stunting crew as Slayer (the founder of this stunt).
UPDATE: So people stop asking. I used a Cargobob + Bobcat to get the Scorcher on the roof.
UPDATE 2: Again, so people stop asking. The reason this is unlisted is that it's extremely easy. If you go in game right now, pedal off the roof and lean forwards at a 90 degree angle, you will land this stunt. It's that simple :D.
I've been working on a full length stunt video for over a year now. So, I'd rather be represented by that kind of quality, than something like this. Stick around for that if you want to see something truly special (coming soon). Hope this helps explain :).