I cut up the carcass, neck and odd bits in smaller 2 or 3 inch chuncks, then put them in the hot oven in a roasting pan, until deep golden brown but not burnt. Then place them in a stockpot, cover with cold water, and slowly bring to a very slow simmer. While that's heating up I roast the aromatic vegetables in the oven (chunks of onions, carrots, celery).
Once the chicken is simmering you have to skim the top and if possible defat it, with a laddle and/or a skimmer. After a while you can add the roasted veggies, a bouquet garni if using, let simmer a few hours, strain, cool down in ice until room temp, then freeze or chill in the fridge.
You can also rub the chicken bones with tomato paste before roasting.
Anywhere from 350 to 450 is ok, just look at the color of the bones and when you achieve the deep golden brown, take the bones out. Convection or not, doesn't really matter either, just look at the color.