Well, I will tell you how I did that one. And then I will tell you what I have learned over the last few years and how I do it now.
The one above was charred on 4 sides in a Daniel Boone on Grill Grates with the DB set at 500° for about 5 minutes on each side. The pit was turned down to 325° and I cooked the meat till it hit an internal temperature of 125° dead center of the roast. It was pulled with the temperature gauge still in it, rested, and as soon as the temperature started to drop, was served...On this cook it peaked at 138°...
Now days for Roasts, I still sear it, but I cook it at about 240°, takes longer, but is more gentle on the meat fibers and does nor require anywhere near as long a rest. It also is a more consistent temperature through the Roast!
Large roast are all about temperature for me anymore...Just to easy to accomplish with todays thermometers...