also - garlic; yes or no? i've not generally put garlic into stock but i've spent the last 20 mins doing a quick resume of internet recipes and some wild types put a clump of garlic in.
I usually go 1 carcass, 2 carrots, 2 sticks celery, 1 onion, a few peppercorns. 80ish° for a few hours, and doesn't even need skimming. Garlic doesn't really feature.
For a stock stock, I usually leave them raw. I'll only roast them if I want the different flavours.