I'm no lawyer but my understanding is that once arrested for domestic assault, accepting any plea to any lessor charge i.e. simple battery or assault is still a legally a conviction for domestic violence. I would see an attorney specializing in guns because it's probably going to take some expertise to work through the roommate angle and you're likely to do far far far more harm than good to your case by handling this yourself.
Essentially congress and the SCOTUS adopted the premise behind the Napoleonic Code that it's far better that 10,000 innocent men be stripped of their rights as citizens than one domestic abuser have access to a gun.
Note that some jurisdictions have expanded their domestic violence statutes to include yelling or walking outside (away) and punching a wall.