re: Gumbo with small brown clumps.

I've never had that happen. My stock is always simmering when I add the roux by spoonfuls to it, stirring each time. My roux is usually hot or at least pretty warm, as well, because I start adding it as soon I've finished simmering the vegetables in the roux.

Some folks say add cool roux to hot stock. I've never concerned myself with the roux temp. I just add it slowly to the stock and stir well between each addition.