Add the fat to a roasting pan or pot over medium heat. Place in the shallots, celery, carrots, garlic, parsley, thyme, and rosemary and lightly brown while stirring every 20 to 30 seconds.
Next, stir in the flour until it is completely combined to make a roux. Pour in the stock or meat juices and turn the heat to high while stirring to mix in the roux while occasionally stirring.