ALWAYS use equal parts oil and flour. Some people like to make their roux in the microwave. However, I think that nothing beats the texture and consistency you can achieve by making the roux in a cast iron pot. For a small batch of gumbo to serve about 8 people, make a roux with 1 C oil and flour. Cook stirring constantly until a deep dark brown. Next add chopped vegetables and seasonings such as onions, garlic, bell pepper and celery to the roux and cook slowly until tender. Add warm stock ( usually fish, shrimp or chicken) in a slow steady stream whisking to blend roux and vegetable mixture. Add salt, pepper and herbs such as thyme and bay leaves and cook at a medium heat to reduce and thicken the stock and make certain that the “floury” consistency is cooked out.