Roast turkey didn’t become de rigeur at Thanksgiving dinner until the nineteenth century. Before Thanksgiving became an institutionalized celebration of Americanness it, and its menus, were a more ad hoc affair, featuring whatever any family thought appropriate. By the 1850s New Englanders had more or less standardized the holiday in an attempt to recapture something that had been lost since colonial days, some simplicity or integrity or je ne sais quoi. Turkey, being identifiably American, fit the bill, and we’ve been stuck with it ever since.
I am not, however, going to give you a recipe for roasting a turkey. Roasting a turkey is a simple affair if you are not inclined to be perfectionist about it, which you ought not be on Thanksgiving, for the simple reason that with all that family around, you are going to need to be too drunk to follow through on your perfectionism anyway, and will therefore inevitably be disappointed. You are, moreover, almost certainly not going to roast a turkey next Thursday. You are far more likely going to bake the thing, which is an altogether different matter.