Roast for one is a waste of time & effort imo.
A roast requires very little effort regardless how many or few people you’re cooking for. Potentially a lot of washing up, but theres very little involved other wise. Cooking for few people means you can just prepare everything in order, bunging it in the oven as you go.
If you look up Jamie Oliver xmas recipes theres a nice roast veg platter, 4 different veg roasted together in different flavours, that plus pots roasted in red wine vinegar and a meat lump of your choice does the trick
Duck is a good roast for one. I’m usually catering for vegetarians at xmas so cook a nice veggie main event, the stuff above and a duck for me. The flavours in the veg are sharp enough not to have to do any backflips with the duck, just roasted fairly plainly with a gravy made from the juices and red current jelly.