I've cooked my prime rib like this for years ... always delicious!! One rule of thumb - if you're using a smaller roast - cook at 500F for 5 minutes PER POUND of meat (so a 5lb roast would cook for 25 minutes) and your roast will turn out perfect every time.  -  18 Dec 2002  (Review from Allrecipes US | Canada)

Although this would "seem" simple enough, I sit here, fuming, because the lack of experience on this board continues to befuddle me. I purchased a 3.5lb boneless rib roast. I let this roast sit for 30+ mins, to achieve room temp. Following this, I rubbed this roast with the mcormicks steak rub, followed by smothering with dijon mustard. Because I wasn't 100% sure HOW to cook this, I placed it in a 500 degree oven for 17mins, covered, following the 5mins/lb @ 500 rule. At 17 mins, the roast hadn't even BEGUN to cook. Uncovered, and returned to the same oven. Mild smoke ensued. Retrieved from oven after 11mins, and let rest to continue to cook. (Approx 15mins) Began to cut roast, and noticed that, although it "appeared" cooked, the inside was still very very rare. It is now BACK IN THE OVEN, over 1.5 hours after the original attempt. People, please, if you have a convec oven, or notice something particular in your cooking, please, please, please post it in your reviews. I cannot give this recipe a decent review, as the instructions (5mins/lb@500 degrees) are, like I thought, simply untrue.  -  22 Oct 2006  (Review from Allrecipes US | Canada)

Loved the garlic and mustard taste. However, as one reviewer noted, this is very easy to overcook, which I did the first time. For those of you who prefer prime rib medium rare or less......I suggest: Preheat to 400, Roast for 1 hour in OPEN pan, in center of oven. Shut off for 2 hours (Also, DO NOT open door) Turn oven back on to 375 for 30-35 minutes. Tighly cover with foil and "rest" meat for 15 minutes before serving.  -  20 Mar 2002  (Review from Allrecipes US | Canada)