Turkey stock

Just add it a little at a time and let stir it in until you're ready for more.

The general practice is to have each element at contrasting temperatures. The roux rule of thumb is:
Hot roux + cold liquid
Cold roux + hot liquid

With the dark roux of a gumbo, warm or hot roux seems to be the accepted practice.

When I make it, I let my roux cool to room temperature and add it after I bring my pot to a rolling boil.

But I make my gumbo in a very unorthodox way.