Well you could either smoke it, or roast it. Either way do it low and slow. Cook it till its about 125f for rare. But you gotto do it really low heat, I would cook it at 225 in the oven or smoker. Also season it heavy, get a injector to get some good stuff inside as well.
Ok, so I think I will smoke it, I just called my butcher to ask actually how big it is and its 23lbs.
I am thinking about 7-8 hrs of cooking? at 225°?
maybe I will cut it in half to cut down on the cooking time
my butcher mentioned rubbing it in garlic, buttter, salt etc....
also that if I smoke it, by the time its done it will be well done on the outside and rare on the inside. They also mentioned cutting off pieces while it cooked
Im rather new to smoking things, so this should be fun or a disaster
I reiterate, you've got to use a thermometer. Cooking time is dependent on surface-to-mass ratio, deepest point from any surface, circulation of heat... Lots of things more complicated than weight and temperature.
A probe thermometer would be best, but any meat thermometer jabbed into the deepest, thickest part of the roast is better than none at all. When that sucker hits 120 degrees, pull the meat, and wrap it in foil to rest it before carving.