When cooking a prime rib roast boneless you have two choices. You can either purchase the roast without the bones or you can simply purchase the roast with the bones and ask the butcher to remove the rack for you and tie it back onto the meat.
If you buy the roast without the bones then you will need a rack inside your roasting pan to place the meat on. But if you have the rack of bones tied back onto the meat you simply place it in the pan bones down. The bones will act as the cooking rack so you will not need one in your pan.
Before cooking prime rib roast boneless, be sure and place the roast in the pan with the fat side up. The fat side is always opposite the bone side so if you have the butcher tie them back on he will know to tie them back on where they go, so when you put the roast in the pan with bones down, then the fat side will automatically be facing up.
Before cooking a prime rib you should always allow the roast to set out of the refrigerator for about two hours or until it has reached room temperature before placing it in the oven.
The roast should be cooked in an oven uncovered at 350 degrees. Many people like to sear the roast in a hot (450 to 500 degree) oven for about 15 minutes before turning the heat to 350 degrees F. The only way to know when the roast is done to your liking is to use a meat thermometer. An instant read thermometer is best and should be of good quality. Your prime rib was not cheap so don’t use a cheap thermometer.
The roast should be removed from the oven 10 degrees before it reaches your desired temperature. For example, if you want your roast to be medium rare then it should reach an internal temperature of 135 degrees F. That means you should take it out of the oven when it reaches 125 degrees because it will continue to raise in temperature about 10 degrees during the resting period.
The resting period should be no less than 15 minutes. 20 to 30 minutes is recommended by most professional cooks, and during this resting period your roast should be covered by a foil tent. This will help to deflect the heat back to the roast and not escape too fast.
If you do not let the meat rest then it will not be as juicy. Letting it rest will allow the juices to relax back into the meat, whereas cutting to soon will allow the juices to run out.