Yes you can forgo the roux. I make a paste of skim milk and 2 tbs of flour
for every cup of liquid I want to thicken, Just make sure you let the mixture
bubble/simmer for at least a minute so that the the floury taste can cook out
a bit.
I think I remember a long time ago, Michele talking about "toasting" flour
until it is golden and using that in thickening sauces.
Cheri