OK. Not trying to start a roux holy war. I prefer to use bacon and/or sausage grease and butter myself. Many of the recipes in cookbooks call for vegetable oil. The chef I learned the trick from was working in a commercial kitchen, which translates into huge quantities. Using bacon/sausage grease wasn't really an option due to the quantity required. I'm not sure if the butter would burn at 350 in the oven for 30-60 minutes.