Oh my! You've got to be kidding! DO NOT PUT IT ON A GRILL (yet)! This is simple and excellent eating.
The secret with cooking prime rib is TIME, sear and very slow cooking.
a. Use the seasoning as suggested, salt pepper etc., and serve it up.... or...
b. mix seasoned salt Lawrys (sp?) with beef bullion, onion powder, brown sugar and corn or peanut oil in a blender. It should be a dark brown liquid, keep blending until it starts to jell. Slowly add water, the color will change to a lighter brown as it thins a little. When you taste test it, it should be very salty and sweet and still thick! (from a famous resturant who's speciality is prime rib and lobster)
Cover the roast with this stuff, smear it all over and then fire up the grill, as hot as possible! HIGH heat to sear! Essential for any prime rib preparation - sear first! About 3-4 minutes each side(s) and ends - it'll get crispy or carmelized (you WANT that)
If you don't have a rotisserie - Place it in a pan (to collect the juices) Either turn down the grill (if gas), close vents (if wood) and get the cooking temp down to 175-200f. Cook for 4-6 hrs under LOW heat, below water boiling heat. Use a stick thermometer and check for an internal temp of 165f or so. The meat will have pulled slightly off the bone, serve by cutting between the ribs.
If you do have a rotisserie - have some cotton string handy to tie up an loose spots (just in case). Low heat (200f) and let it go as long as you can stand your stomach growling - the smell is gonna make you VERY hungry, hopefully you can hold out for 3 hours... cut between the ribs to serve.
If you have a smoker - HICKORY!!! follow any of the above, sear and slow cook. And don't be afraid to move the prime rib from the grill to an oven if you can't regulate the heat. Better to have it perfect than wish you had!
BTW - the oil will burn, leaving a crusty coating of brown sugar & seasoning mix behind - you WANT it to sear fast, don't let a grill flare up bother you, let it burn HOT! The addition of water helps control the burn a little.
Now why don't I get a perk like that at work any more....?