"Why do some men say they believe in TRADITIONAL GENDER ROLES?"
I suspect because they remember how well society functioned like 50 years ago, and they believe that socially held gender roles played a significant part in that. Say what you will, but the nuclear family was probably the greatest family unit we in the Western world have ever known.
"But then if a woman says she wants to become housewife, then they call her gold digger, no ambition, lazy, loser?"
I suppose it's possible that "some men" do in fact view housewives in that manner...however I certainly have never known any men who view them in that manner.
I do however believe that men who work outside of the home expect that if they have a "housewife," she should attend to the housework if he is the one out working and earning the money that keeps them housed and fed.
And frankly in this day and age, with the technology we have in the developed world, I believe that is entirely reasonable!