No, just do like it says. The key is to not ever open the oven door. You can put a thermo in it after it comes out if you want to make shure. A friend from work has a sister that is a chef at some fancy resteraunt in San Fran , and she did not belive this would work and would not let him wreck her meal ,so they cut the roast in half and cooked it both ways. Hers was f'ed up and he was a hero for the day. She now impresses her friends with her inovative style of Prime rib. I say hit the easy button.
Sounds easy but I know I would want to open the door because I can't!