Transfer roasted turkey to a large platter. Pour juices from pan into fat separator. Set aside to separate, about 10 minutes. Reserve fat.
Heat the Turkey Stock in a medium saucepan over low heat. Place roasting pan over medium high heat. Pour Madeira into pan, let bubble (raise heat if necessary), and scrape bottom and sides of pan with wooden spoon to dislodge browned bits. Remove from pan and reserve with pan juices. Return 2 ounces reserved fat to roasting pan, sprinkle flour into pan and cook over low heat 2 to 3 minutes.
Slowly whisk in heated stock and reserved pan juices. Increase heat to medium high. Add rosemary and season with salt and pepper. Cook until thick and the gravy coats the back of a spoon, 10 to 15 minutes.
Strain gravy from pan through very fine sieve. Adjust seasoning. Keep warm in heatproof bowl over a pan of simmering water or serve immediately.
Turkey neck and giblets (heart and gizzard), reserved from turkey
1 medium onion, cut into large chunks
2 celery stalks, cut into large chunks
2 carrots, scrubbed and cut into chunks
6 sprigs fresh flat-leaf or curly parsley
2 to 3 sprigs fresh thyme
1 whole bay leaf
1/2 teaspoon whole black peppercorns
7 cups cold water
Rinse neck and giblets well. Combine turkey neck and giblets, onion, celery, carrots, parsley, thyme, bay leaf and peppercorns with 7 cups cold water in a medium stockpot. Place over high heat; bring to a boil.
Reduce heat to a simmer and cook for 1 1/2 hours, skimming any scum that floats to top as necessary.
Pass stock through a sieve lined with damp cheesecloth; discard the solids. Let stock cool, and refrigerate until ready to use.