grilling a prime rib roast

Hi, I am grilling a prime rib roast using infra red cooking. the roase is about 9lbs and I'm not sure how long it should cook or what kind of marinade I should use.

I can't speak for infra-red cooking, but a prime rib is a pretty subtle flavor. If I oven roast, I might encrust it with herbed rock salt to get the outside tasty. I think it is too thick a cut to actually marinate (and is tender enough already). If I indirect grill, I'll spray some oil on it to make sure the crust browns nicely,but IMO you don't need to do much to a rib roast to make it taste good.

Just don't overcook it, and DO NOT FORGET to let it rest a good 1/2 hr. before carving lest all that delicious juice run out and leave you with grey meat !!