It is just that I once partly cooked a pork roast and then finished it off the next day and everyone had food poisoning
That was your problem. You can't partly cook meat and leave it til the next day. Certain recipe for food poisoning because the bacteria wouldn't get killed with the first cooking but reaches a nice warm temperature that's ripe for multiplying. Then you store it for 24 hours to multiply some more before heating again, to multiply again until it finally reaches a temp to kill the bacteria. The food poisoning isn't always the bacteria itself but the toxins that they produce as a byproduct. You can eat food that has been heated enough to kill bacteria and still get sick from the toxins that don't get removed with heat.
If you want to do it ahead, I'd cook it through, cool it quickly and then slice and heat again the next day. I would think a rolled pork roast would be easier to do this with than a whole turkey that is prone to drying out anyway.
Do you have a BBQ or webber that you could borrow. I prefer to cook fresh on the day and roast pork is delicious done on a webber.