I definitely agree with Jeff's assessment. I also used to be a contractor, and I'm not sure I'd trust a preexisting roof structure to handle a hang, at least not without beefing it up a bit. Most stick-built roof systems are designed without a huge amount of stress leeway above their normal operational load. Engineered roof trusses might take it, but I'd be leery. I think the best bet would be to hang from a good solid floor/ceiling joist, like one would find in a garage with a living space upstairs, but I'm still not sure I'd try it myself.
"Physics is the only true science. All else is stamp collecting." - J. J. Thompson