I want to beat up my roommates friend
Why do you feel the need to beat up your roommates friend?
Cause I'm a really angry guy and they deserve it.
You should not beat up your roommates friend. Even if they have made you angry you should try to be the bigger person in this scenario.
I don't like the way she looks at me.
That's no reason to beat someone up. If you don't like the way she looks at you, then you should politely ask her to stop.