Your larger problem is that your lease isn't with your roommates, but is with the landlord. The fact that you chose bad roommates doesn't affect your obligations to the landlord in the event that your roommates fail to pay the rent or cause damage to the apartment. Perhaps your landlord will permit you to make some form of one-time payment to be released from the lease. You may still have some obligation to your roommates, but from what you have said they won't look very sympathetic if they try to enforce it (and you would appear to have some good defenses to any claim they might bring).

