Food safety regulations say that a turkey should be roasted at a temperature no lower than 325 F. It is possible to roast a turkey at various different temperatures, depending on the desired result, cooking time and size of turkey.
Both methods will work, but roasting a turkey at a low temperature for a long time will have a different result to roasting it at a high temperature for a short time, according to Epicurious. This food website suggests a range of temperatures for different sizes of turkey. For example, a turkey that weighs 18 to 20 lbs. should be roasted at 425 F for 3 1/2 hours, or at 325 F for 4 1/2 hours, or somewhere in between that range.