Wish I'd seen your question earlier -- and glad everything turned out well.
Time/temp for large roasts doesn't depend entirely on weight. The question is really, how long is it going to take for x amount of energry to get to the center of the meat. So, you have to figure out how much the roast would weigh if it were no longer than it is wide.
But you have to add a little extra time because the extra mass does use some energy. Figure the extra as half.
In the case of a beef rib roast (with cap) the length = width rule is about four ribs long. FWIW, the full rib is eight bones, and the "prime rib" six; and BTW, that's what "prime rib" means -- the middle of the rib.
Supposing your 14 lb roast was eight bones, I'd figure four ribs at around 7 lbs (clever, no?), the remainder at 3.5 and cook accordingly. If I cooked at 375, that would be 12 mintues a pounds to medium rare (125), or 2 hours, 6 minutes -- call it 2 hours. The 2 hours is just a prediction which should be interpreted as: check with an instant read at 1hr 45min.
Although you cooked your roast at two temperatures, I think you can see that my method for figuring time/temp predictions is consistent with your experience. Still, nothing beats a thermometer.