Don't even think about using that stuff in the can. This enchilada sauce is too easy to make and it tastes so much better. Use it on enchiladas or burritos.
If you don't have the roux or don't feel like making it, you can make a quick roux in a pot with 1 tbsp each of oil and all-purpose flour. Add your puree to the pot after the roux has browned and simmer 5 minutes.