I did without. I think that debate is cooks preference. It might help stay a little warmer if tented, but it's a big chunk of meat that's going to hold a temp for a while. If you have a good crust on the roast, the steam from tenting can make it soggy.
Discussion
Prime rib went well! Perhaps a bit rare for my familys preference. My 'trustworthy' in oven therometer betrayed me mid-cook, jumping from 100 degrees to 130 instantly at one point. Luckily i stayed calm, temp'd it with a digital thermometer and it was around 110. Back in the oven for 10 more mins and 🤌🤌🤌