You can thicken any soup with a Roux. You can make it days ahead of time and store it in your refrigerator. Melt 2 tablespoons of Butter and whisk in 2 tablespoons Flour. This will thicken a small pot of soup. If you want to make a chicken gravy add 1 1/2 cups chicken broth and 1/4 teaspoon each of salt and pepper.
If you want to make a gumbo you will cook the roux ( 2 tablespoons bacon fat and 2 tablespoons flour) until it turns a mahogany color. Stir often so it doesn't burn.
You can make a roux from any fat and wheat flour.