OK, it's actually an interesting idea, I would never consider to make a soup with leftover bones of a roasted chicken, until I've read it here. Usually I do the opposite, I boil a chicken to make chicken soup and I use the meat to make another dish.
Most of the time I use my leftovers to make soup. I have a lturkey now that I will use to make soup, I will take any vegtables in the refrig and add them to the soup broth, cut up an onion and some celery, some times I add potatoes or rice to the mix to make the soup more filling. Leftovers are never thrown out in this house.
Actually that is something I don't do because I think that the leftovers might give a funny taste to the soup. I do love to remix my old rice with some eggs and sausages or tuna, they make a great combination.
Don't forget that any fat left on the carcass will rise to the top of the stock when it is simmering. You can them skim this off with a shallow spoon.
My son is going through a stage of picky eating, so we've had to find ways to save leftovers so that all of the meals I make him that he refuses don't go to waste! One of my favorite ways to recreate leftovers, is whenever rice or pasta is leftover, to mix it into some bouillon or broth (My favorite is Herb-Ox), and make a nice soup out of it. I end up freezing some of it, and it tastes really great. I've found ways to also save bread to by wetting it, baking it, then storing it again. Leftover meat here is usually used in sandwiches depending on what type of meat it is, or used in pasta sauce.
