It seemed a lot of other people had the same idea and a true prime rib was not to be found in Phoenix, so I ended up with two 6-8 pound rib eye roasts from Costco. Someone else has since fixed this with a tenderloin roast and said it was good too. SO.... here's the recipe. It's worth the work!
S-P's Mother's Day Rib Eye Roast
Place the roast on a wire rack over a cake baking pan.
Pour balsamic vinegar over it and rub it in all around the roast on all sides.
Cup your hand and pour about an inch and a half diameter mound of coarse sea salt in it. (I bought the coarse Mediterranean Sea Salt grinder from Costco and had to break the top off, but any VERY coarse sea salt or Kosher salt should do fine... DO NOT use fine table salt or grind the salt onto the roast, it HAS to be put on coarse.)
Sprinkle the salt liberally and uniformly over the roast on the one side and pat the salt down lightly so it stays put. Turn the roast, pour another mound of salt and salt the other side and ends. (It looks like a lot of salt, but don't worry, this is what it takes for the prime rib crust).
Prepare a mixture of two heaping teaspoons of Montreal Steak seasoning, a heaping teaspoon of red chili powder, a level teaspoon of paprika, a level teaspoon of garlic powder. Sprinkle this over the roast on all sides, covering evenly and liberally (but don't use all of it...that's too much, you can use the leftover for steak seasoning or making the prime rib "Outback Style" when serving it... see the end of the recipe below).
Take a squeeze bottle of honey and drizzle honey over the whole roast in lines about a half inch apart creating a "checkerboard pattern" with the honey.
Cover with foil, put in the refrigerator and let marinate for about 8 hours (overnight).
Take the roast out of the refrigerator at least TWO HOURS before cooking to bring to room temperature (this is important!)
Set the oven to 200 -225 degrees and put the roast in on the wire rack over the cake pan you used to prepare it on, leave it uncovered.
Let cook for about 6 hours (depending on the size of the roast... the large one today was about 8 pounds).
You cannot use "rule of thumb minutes per pound" to cook a roast. BUY A MEAT THERMOMETER! Get an "instant or rapid read" thermometer at the grocery store for about $9.00. Check the roast after about 3 hours and keep an eye on the internal temperature.
No matter what the thermometer recipes say, rare is 110 (NOT 130-40!), medium rare is 120, medium is 130, etc.) You can always cook it more, you can't uncook it.
Remove the roast from the oven and let it sit for about 10-15 minutes to rest before carving.
(You can carve the roast and heat a cast iron skillet (it has to be "smoking hot"! and sear the meat to make it a little more done if necessary...if you sprinkle it with a little of the leftover Montreal seasonings and sear it in a smoking hot skillet with a dab of butter, that's "Outback Style".)