The bulk of the roof can be assumed to be oriented to the sky, or it wouldn't get much sun and be of no concern. So it will radiate towards the sky mostly. The

The bulk of the roof can be assumed to be oriented to the sky, or it wouldn't get much sun and be of no concern. So it will radiate towards the sky mostly. The infrared radiation will indeed go out in all directions. The way I understood it there will be less of it, because the roof is cooler. So if this material replaces a traditional surface, you will get more visible light scattered your way, and less infrared light.