Will I go to jail because of my roommate's case?

What? I don't see why you would go to jail for your roommate's DUI - unless you were hanging out the car window shooting at the cops when he was pulled over.

If your roommate was driving, underwent a sobriety test, and then was arrested for a DUI, then the arresting officer either determined that he failed the sobriety test, or he believed that he had probable cause otherwise to arrest your roommate for a DUI charge. Based upon this, the officer apparently determined that your roommate was A) driving the vehicle, and B) that he was inebriated to a degree that made him incapable of safely operating a vehicle. Because the officer has determined that your roommate was driving the car, there shouldn't be any way that you could be charged with a DUI. Even if the charge against your roommate is dropped because they determine that he was sober, they can't then charge a non-driving passenger with a DUI. Additionally, if your roommate was arrested and is in custody for a DUI, then I don't foresee them dropping the charge. The prosecutor may eventually dismiss the charge if it can be shown that he did indeed pass all sobriety tests, but if he has already been arrested, then the charge will likely remain until it is disposed of in a court of law.