Here's how I would do it. If you're using Kingsford, light about one full chimney and get it good and glowing, dump those coals on one side of the charcoal grate, put a drip pan on the other side of the grate.
Sear your roast directly over the coals and get a good sear on it, on all sides, then move directly over the drip pan, put the lid on, crank your bottom vents until they are almost closed, get a temp of 325-350 in the grill and take the roast to an internal of 125. Pull loosely wrap in foil and let rest 15-20 minutes.
Should be a nice med rare. Throw a chunk or two of wood on the coals and put the lid vent directly over the meat.
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Rubbed, Smoked, and Sauced Competition BBQ Team-
22 1/2" WSM, 2 18 1/2" WSM's, 22 1/2" Weber Kettle