Hi Dr. BBQ:
What is the cooking time to slow smoke a 15-pound rib eye roll at 220 degrees to medium?
Timing isn’t going to work too well with something like that. You’ll need to monitor the internal temp of the meat. For medium you’ll want it to reach about 150 and then be sure to let the roast rest for 20-30 minutes. At 220 I’d guess it’ll take about 6 hours but that’s really just a guess.