Help! I forgot to take a 22lb prime rib out of the refrigerator to get it to room temp. I cut it in 4 pieces. 30 min per pound for medium?

Have a look at this thorough article from food network about how to cook prime rib.
Adjust the time depending on how hot your oven will be...not always half an hour per pound.
If in doubt, check a while before you think it will be done, lest it cook too much.
If you have a meat thermometer, aim for 160F or 71C temp...take out from oven, rest, then carve.
Good luck for your Christmas dnner!

https://www.foodnetwork.com/how-to/packages/food-network-essentials/everything-to-know-about-prime-rib