Roasting a chicken, I usually simmer the giblets (excluding the liver) with a few vegetables in a small saucepan, and add this stock to the juices in the roasting tin.
This weekend, I put the giblets and the vegetables (an onion and a carrot, both sliced, along with some garlic cloves) in the tin with the bird, roasting them alongside it for 30 minutes at gas mark 6/200C. Then I poured in half a glass of white wine, stirring giblets and vegetables into the liquid, and turned down the oven to gas mark 2/150C for a further 90 minutes (it was a 2kg bird). Every so often, as the liquid evaporated, I added a little water. I doubt whether I used more than 150ml liquid in total; the chicken contributed its own juices.
What was left at the end of the two hours was, strained, our gravy - nothing else added.
My reservation about this technique is that a steamy atmosphere in the oven might cook the chicken too efficiently, drying out the breast. But that was not a problem in this instance.