For average appetities allow 225-350g (8-12oz) of pork on the bone, and 150-175 g(5-6oz) of boneless pork. You can cook quite a small roast successfully because the outer layer of fat will keep it moist, but a larger roast is more economical and can be eaten cold next day.
Reheating cooked Pork
Never reheat pork whole. If you use cold slices or cubes as a basis for another dish, it is essential that the pork is recooked right through (that is, the meat reaches boiling point) and is not just warmed up, in order to kill any bacteria that might have formed.
Refer here ** Healthy Roasted Meat ** and ** Chinese Cooking **