Crumble the sausage and brown it in the skillet. Use a potato masher to break up the meat until you have fine morsels, or leave some chunky as desired.
Make a roux. Add the flour to the skillet and cook, stirring, until the flour turns brown and blends in well with the meat. If there are some drippings still loose in the pan, add another tablespoon of flour. You'll want it to be dry, not greasy. Continue adding flour as necessary.
Add milk and stir well. Cook over medium heat for 10 to 15 minutes or until thickened. Continue adding ¼ cup of milk until the gravy is thickened, but not pasty. Season with salt and pepper to taste. Serve over hot fresh biscuits.