I'm planning to call my Roommates mom a Stepford Wife
Why are you going to call her that?
Because she acts like a Stepford wife
You really shouldn't call your roommate's mom names like that. It will be seen as rude, and she would certainly show you more respect than that. Disrespecting your roommate's mom will make your roommate very upset with you.
But its true
It may be true, but she may have grown up in an earlier time when this kind of behavior was expected from mothers. You have nothing to gain from calling her names, and quite a bit to lose if you upset your roommate or her mother. It's best just to keep your feelings to yourself.