Pour roasting pan juices into a gravy seperator to remove fat. Taste to make sure that juices are not overly salty and are suitable for use in gravy. (Juices should not taste saltier than canned low-salt chicken broth.).
Add juices to a glass measuring cup. Add broth to measure 2 cups. Transfer to a suacepan. (If more than 2 cups of pan juices, boil until reduced to 2 cups liquid).
Cook bacon in skillet over medium heat until brown and crisp. Remove bacon (save for another use). Discard all but 2 tablespoons drippings from skillet.
Add flour. Whisk over medium heat until roux is golden brown (about 3 minutes).
Whisk in broth/juices. Bring to a boil, whisking occasionally. Reduce heat to medium-low.
Mix in vermouth and sage. Simmer until thickened (about 10 minutes).