I've found a good turkey roasting app in time for Thanksgiving! It's called BB Turkey Master. OK, I haven't had the chance to test it on turkey yet but it can plan beef, pork, lamb, and chicken too. I tried it with beef and chicken and using the cookplan the app made they both came out perfectly, so I'm going to assume it's just as accurate with turkey.
I never knew there were so many considerations when roasting a joint of meat! It asks whether the meat is boneless or bone-in, what type of oven you have (what's a "fan oven" anyway? I'm assuming that since I don't know mine must be conventional), and when you want to serve.