A dark roux in development a white roux a roux-based sauce roux (/ ruë /) is a mixture of flour and fat cooked together and used to thicken sauces. [1] roux is typically made from equal parts of flour and Ò€¦ When youÒ€ℒre making a roux, you are combining butter and flour to thicken sauces and create deliciously rich consistencies.