I've tried making a roux using canola several times. It didn't ruin it but the roux just isn't as smooth as with other oils. Somebody mentioned lard; I used it ONCE to make roux. The roux cooked up and browned beautifully and had a smoothness you don't get with other fats. I was making a turkey stew/soup that turned out great. Not real healthy, don't use it much but man! it's good.