Remove roasted meat from roasting dish and place on a chopping board for carving.
Add a couple of cups of boiling water to the crusty dish and leave to sit for a moment, attacking with a fork to help the deliciousness dissolve into the water. Pop dish over element on a medium heat and add a good splash or white wine (if cooking white meat) or red wine (if cooking red meat) (optional).
If you dont have a lot of tasty crusty stuff in the pan you might want to add a stock cube (depending on the type of meat) as well.
Add milk until you get a nice creamy colour (use cream if you are being super naughty!). Add a tablespoon or so of flour (any kind) and whisk lumps out with a fork or whisk and continue to heat until it begins to thicken. Make sure it gets a good cookn to ensure the flour dissolves fully. If it doesnt thicken add a wee bit more flour until you get a good consistency.
Season if necessary - you can use a bit of soy if you want rich colour too but be careful not to add salt if you do.
Tip: If you throw a rough cut onion and some whole unpeeled garlic cloves into the base of the roasting dish before you roast the meat you'll get lots of flavour in the juices (as per the roast chicken recipe).