pour some kitty litter on it, play some chubby checkers, do the twist.

You can also try powder clothes washing detergent.
It absorbs the grease and helps wash it away.
Pour detergent over the area and let it sit a few hours, then hose off.
Repeated applications and even some scrubbing may be required.

The best thing I've ever used has been Gunk Engine Degreaser. I use it on the garage floor all the time. Squirt it on, let it soak for about 2 minutes, brush with an old tooth brush and hose it of. When it's dry, you'll never know it was there.

Try oven cleaner. Leave it overnight and hose/scrub it a bit.

What?? and they didn't offer you any fajitas????

The only thing you should do is call the roofer and ask him to send someone out to clean up their mess. The homeowner never should have to clean up after the workmen.