Actually, if you make a traditional white sauce you would use a roux anyway. My mum makes a lovely quiche by making a thick white sauce containing egg yolk, then whisking the egg whites and adding them. Sorta like a souffle in a crust. Lovely.
not a soufflé, no you need eggs for that but the fat/flour make a roux anyway you could always add stock instead of water and make a 'velouté' sauce instead of a white sauce