(quoted from post at 18:17:56 03/26/15) It is also called "Sawmill Gravy" and is a staple for biscuits and gravy, also very good over boiled potatoes as one of my favorites at grandmas growing up. I, like grandma, eyeball it so I don't have a recipe but Alton Brown did one on his show, heres that recipe:
http://www.foodnetwork.com/recipes/alton-brown/sawmill-gravy-recipe.html
he also has a link to biscuits, which are a very specific item I don't make from scratch.
a couple of key things. Depending on how you want to use the gravy, you can crumble the sausage and use it all or reserve 3/4 of it for a less meatier gravy (grandma served as patties with the aforementioned boiled potatoes, then the gravy went over both).
depending on your sausage, you may want to drain some grease, you need about 2 tablespoons, but ideally you want near equal ratios of flour and grease. this is the basis for any roux, you do not want the flour/grease mixture to get very dark before adding milk, but you do want it cooked.
DO NOT USE SKIM MILK, even 1% is a bit lite. 2 percent is decent for gravy making.
Sausage selection is important, you need enough fat to make sure you get sufficient grease. The sausage will also impart most of the gravy's flavor so pick a sausage that compliments the meal. I avoid "flavored" sausage like maple breakfast sausage. Instead I prefer a mild or medium Italian or straight breakfast style, something with a fair bit of herb and spice. Taste the gravy before adding salt and pepper, as you may not need much if any seasoning.
It won't look like much when done, but its good stuff.