I almost always roast my older roos. I try to butcher by 16-18 weeks, but that doesn't always happen. I do mine in an electric roaster at 250 for 3-4 hours and I make sure the roaster never gets dry. The older they are the longer they need to cook, I find them to have more texture but never tough. I do rest my birds in the refrigerator for 3 days before I freeze them.