I'll start with my own disaster.  I picked up a bone in (two bones) prime rib roast that came in at 4.91 lbs.  Got it for a steal at $6.75 per lb, I usually pay around $10.  The marbling looked awesome and I really thought I was getting a great cut.  I was cooking on Christmas eve so I unpacked i, let it rest uncovered in the fridge with a simple salt & pepper rub on it for 24 hours.  I pulled it out around noon on the 24th to come to room temp before going in the oven in a few hours.  I made up a simple herb butter mix that I rubbed it with before going into a 200 degree oven (internal temp of 45 or so at this point).  I should mention, I was using the serious eats method of cooking low and slow for a few hours until I got into the 120 degree range and then searing off at a high temp to get an optimal crust.  It seemed like we were on track and I pulled it out after 3 hours or so at 122.  I didn't remove my electronic probe but I tested it at varying depths and got everything from 121 deep to 131 shallow.  I was thinking this was right where I wanted to be as I would get some carry over and get me close to medium rare to medium range.   It sat for 20 and then went back in at 500 for about 10-15 minutes.  I didn't bother monitoring temp any more at this point which I regret.  I took it out with a beautiful crust and began to serve.  I had to deal with less than optimal carving knives my brother had and found it nearly impossible to get through a fatty section right in the middle of the roast that ran the entire width of the roast.  I was basically hacking pieces off and it was more rare to medium rare for the most part.  I know some of you may be into that but that's not family's preference.  I am not sure there was one thing that caused my problems, rather the combining factors of the cut I bought, bad probe placement perhaps and inferior carving tools.  

Edit: Heres a pic after  did the salt & pepper rub
user
Prime rib, everything that could go wrong did despite a methodical plan.
assistant
I'll start with my own disaster.  I picked up a bone in (two bones) prime rib roast that came in at 4.91 lbs.  Got it for a steal at $6.75 per lb, I usually pay around $10.  The marbling looked awesome and I really thought I was getting a great cut.  I was cooking on Christmas eve so I unpacked i, let it rest uncovered in the fridge with a simple salt & pepper rub on it for 24 hours.  I pulled it out around noon on the 24th to come to room temp before going in the oven in a few hours.  I made up a simple herb butter mix that I rubbed it with before going into a 200 degree oven (internal temp of 45 or so at this point).  I should mention, I was using the serious eats method of cooking low and slow for a few hours until I got into the 120 degree range and then searing off at a high temp to get an optimal crust.  It seemed like we were on track and I pulled it out after 3 hours or so at 122.  I didn't remove my electronic probe but I tested it at varying depths and got everything from 121 deep to 131 shallow.  I was thinking this was right where I wanted to be as I would get some carry over and get me close to medium rare to medium range.   It sat for 20 and then went back in at 500 for about 10-15 minutes.  I didn't bother monitoring temp any more at this point which I regret.  I took it out with a beautiful crust and began to serve.  I had to deal with less than optimal carving knives my brother had and found it nearly impossible to get through a fatty section right in the middle of the roast that ran the entire width of the roast.  I was basically hacking pieces off and it was more rare to medium rare for the most part.  I know some of you may be into that but that's not family's preference.  I am not sure there was one thing that caused my problems, rather the combining factors of the cut I bought, bad probe placement perhaps and inferior carving tools.  

Edit: Heres a pic after  did the salt & pepper rub
user
I made a bone-in prime rib, cooking it slowly and low and slow with a salt/pepper rub, I pulled it out to room temp around 3 hours into cooking at 122 it came out medium rare
assistant