Look at sheet metal roofing, too - its likely cheaper, definitely lasts longer, and radiant heat really isn't a problem. In some ways its cooler than the Ondura products (a popular used to be fiberglass and asphault brand, now I don't know what they use as reinforcing fiber) because the metal reflects so much light, unlike the darker material colors of other roofing, and because its so thin it has very little thermal mass, so good air movement underneath carries away most of the heat before it can radiate far.
A while a go, I took a thermo probe to my coop. I want to say the roof was 2.5* hotter than the native air underneath in direct sun, on an 80* day. By the time I was 6" from the roof, the difference in temperature was less than half a degree.
Plan to test it again in full summer, full sun on a 95 day.