Dark roux are usually made with oil or bacon fat and flour. The scent of a good roux is so strong that it stays in clothes until they are washed. The scent is so widely recognized in Louisiana that others can tell if someone is making a roux, and often infer that they're making a gumbo.
Dark roux aRE UsuaLly mAde with oil OR bacoN fAt And fLOur the scent of A GOoD roUx IS SO strOng tHat IT STAys in cloThes until ThEy ArE Washed THe sCEnT IS So widElY rEcoGNIzed In loUisiana That otHerS caN tell If soMeonE IS maKing a RoUX anD oFteN infer thaT tHey'Re maKInG a GUmBo