Am keen this year to prep as much as I can for Christmas dinner before the day. Any tips please? Am especially keen to get the roast potatoes all done and dusted but I can't imagine serving up re-heated roasties from the microwave! Partner away on the day, small oven (no Ninja!) a microwave and old, four burner gas hob. Does it all have to be re-heated in the microwave? Thank you!