Yes, absolutely, you can do that. Be patient with the bones - you don't even need to cut them up - slow temperature - maybe 250° to 275° all day long, turning occasionally. The idea of roasting slowly brings out more flavor - some recipes say use a 400° for 20 - 30 minutes and I consider that browning versus roasting. The stock that they make is excellent. The best stock I ever made though was by roasting a smoked turkey carcass and then using that to make stock - boy was that good.
Here's how I make mine: (please accept my apologies if I'm telling you something you already know :? )
Add your roasted bones to a large kettle of water being sure to scrape up anything that has stuck to the bottom of the pan too.
Very large onion, cut in half (skin can stay on) and place on griddle or skillet with very little oil and cook it until it goes a couple steps beyond carmelizing - almost burned. Throw that in your stock - skin and all.
I'll take a handful of washed fresh parsley, thyme stems, carrots, celery, and tomatoes (tomatoes cut in half (I usually use 2), if they are slightly "aged" that is even better.
Once the stock comes to high heat you don't want it to boil after that - only slow simmer. As the foam comes to the surface skim off. Just keep skimming and simmering. DO NOT STIR - you want all the dirt and debris to fall to the bottom, which will leave you with a nice clear stock. Don't put a top all the way on it either, keep a little heat escape route. I do mine pretty much all day or all night. It's easier during the day because I can stay on "foam watch" easier.
Once done (and do not salt or pepper either) gently pour into a cheese cloth lined strainer but do not pour the last part that is in the bottom of the pan, that is where the "debris" has fallen and you don't want it clouding your broth.
That pretty much sums it up - if you ever get ahold of a smoked turkey carcass make good use of it (or you can send it to me
(just about any scraps from any vegetable can be used in this stock - asparagus ends, green pepper ends, just the ends of onion that you use, celery ends, etc. and any herb stems that you are going to throw away).