If there still isn't enough liquid, add homemade or low-salt chicken or turkey stock. Tailor the gravy to your taste. While the technique I've outlined makes a delicious gravy, you can embellish on it without muting the flavor of the roast. For a luxurious touch, stir in 1 or 2 tablespoons of soaked, drained, and chopped dried porcini mushrooms or morels. Strain the soaking liquid through a coffee filter and add that, too.
Roasted garlic adds great flavor to gravy and can act as the thickener.
Work the roasted cloves through a food mill or strainer to extract the pulp and stir it into the gravy. My mother's favorite addition is the cooked giblets and neck meat. She'd chop these finely, but not too finely, and heat them in the gravy just before serving. Peterson is a contributing editor for Fine Cooking. Used by permission.