Gee, for a gravy you'd usually need to have roasted something hefty enough to leave juices and caramelised matter.
Take the roasting pan with all of this in. Heat it up real hot on the hob and pour in some appropriate wine, or chosen alcohol, or liquid stock or even just water if you're being boring.
While the liquid boils, scrape up and mix up the stuff and that's your basic. You may choose to add in your roux for thickening, perhaps a spoonful of jam to add gloss to the gravy.
Pour into an adequate receptacle afterward.
This has been your strange wander by post. Cheerio.