How long will roux keep?
Surely you figured something out by now, but here is what I would do. First, look closely and carefully for surface mold. Look around the rim of the container. If that is clear, smell the oil for rancidity. If it stinks, throw it out. At this point, it looks good and it smells good. I can't imagine a dish where the roux is not thoroughly heated, so unless you are pioneering some kind of cold ingredient, cold roux dish, I think you are good to go. The sealed roux in the fridge should behave like a confit and retard spoilage for a while. If you did a dark roux (like a cajun style) it should last a really long time. They sell it in jars in New Orleans supermarkets, and if memory serves, the jar said something like 90 days in the fridge after opening.