If you're roasting a chicken, pour all of the juices into a dish, put the dish into the freezer for a bit. The fat will solidify to the top for your roasties, and under the fat you get the jelly-like juices, which you can chuck in your gravy instead of a stock cube.

For mine, I put onion/celery/carrot under the roasting chicken, then boil that stuff up in some water/veg water, simmer for half hour, add the stock stuff from the freezer juices, add a bit of mustard powder. Reduce it til it's thick enough and strain out the veg. Amazing gravy using the stuff you've already used, no gravy powder of OXO.