Suitable oils for roasting chicken at high temperature in cast iron

Omega-6, omega-3, and other polyunsaturates will likely be kaput anyway after cooking at 230°C, so oil selection criteria valid for finishing/salad/cold cuisine oils should not be blindly applied here. What will remain of the polyunsaturates after that treatment is more likely to be a nuisance in terms of both taste and health than a benefit. So with the exception of peanut oil (see below), a highly refined oil high in monounsaturates or saturates will serve you best.

Oddly, peanut oil, while high in polyunsaturates, is well known to be pretty heat stable in practice, and one of the favorites for high-heat wok cooking for that reason - it will not quickly develop objectionable off flavors or heavily smoke when overheated.

For this kind of use, since you are using the oil at its limits, the actual refinement process used can matter as much as what the oil is made from - eg there are highly refined olive oils that are very heat stable and that you could use well here, however extra-virgin or even low-refinement types would likely fail. The same applies to safflower oil. Oh, and be aware that there are multiple, completely different types of sesame oil - many grocers would assume you want toasted sesame oil if you ask them for sesame oil. Toasted sesame oil would be completely, utterly unsuitable here.

The optimum oil for your needs would probably be highly refined, desodorated coconut oil (not extra virgin, which the often stated smoke point of 177°C applies to) - this is a mostly-saturated, heat stable fat.