Whisk flour, cocoa, and spices together in a saucepan without turning on the heat. Add 1/4 cup of broth and stir into a paste. Slowly whisk in remaining broth and an additional cup of water. Bring to a boil over medium heat and whisk in tomato sauce. Allow to cook a few minutes and thicken slightly to the consistency of tomato soup. Remove from heat and add salt if necessary.