That's exactly what Tony Chachere and Zatarain says.

TONY'S UNBELIEVABLE ROUX Steps: Over medium heat, whisk 1 cup Tony Chachere's? Roux and Gravy Mix with 2 cups cool water. Bring to a boil. After mixture begins to thicken, remove from heat. Continue to stir until well mixed.

I have tried Tony's Roux and it ain't bad when in a hurry. But, my favorite is Zatarain's Instant Roux and Gravy Mix.

Zatarain's® Instant Roux & Gravy Mix adds thick, delicious roux to all your favorite recipes. And it's so simple. Just dissolve in cold water, bring to a boil, then reduce heat and simmer.

2 web sites to order from if your supermaket do not carry it.

http://www.cajunsupermarket.com/index.php?cPath=41_31
http://www.cajungrocer.com/advanced_search_result.php?keywords=roux

All in All Homemade ROUX is the best!!!