My roommate got a job at my restaurant and came home 2 tell me she was fired last night...?

Well, if you think your manager's that irrational, I'd keep my mouth closed so I could keep my job, too. But besides that, sounds like he followed the mantra: the customer is always right, and when they aren't, see above. Just encourage your friend to get another job. There may be more to the story than anyone is letting on, too, so who knows?