Okay, I roast all kinds of birds in the week--cornish hens, guinea hens, chicken, ducks--anything that'll chirp, gobble, or quack--I'm a crazy about them! So I start a bag in my freezer (separate ones for each bird) and just freeze all the bones and carcasses until I have a good amount (for chicken I susally use two carcasses plus leg and wing bones--hens I usually use four carcasses, ducks one because they're too expensive and big to be saving them up in the freezer!!)
So then I take out the hen bones for instance and throw them in a soup cauldron and just cover the bones and carcass with spring water and add:
1/2 tsp. crushed rosemary
1 tsp. thyme
10 black peppercorns
3 bay leaves
A few shakes of salt (I lie, I put a TON in but never mind)
4 stalks of celery
Then I bring it to a roaring boil take the lid off, and then leave it on medium (this is important because any lower and you won't get all the taste out of the bones) for an hour and a half to two hours.
Then strain it and add salt--this is important--the salt will bring the taste to the fore. Cool and then freeze in one-serving jars or in larger ones--I use this for the base broth in my kohlrabi soup--it's gorgeous!
Good luck and enjoy!!