Legal Question in Credit and Debt Law in Ohio

In Ohio, you could argue that the landlord had a duty to mitigate his damages by telling you that your roommate had stopped paying so that you could attempt to find a replacement tenant. Alternatively, you could argue that the landlord waived the right to collect all the rent by accepting partial rent (especially without telling you) and that your detrimental reliance upon his failure to tell you there was a problem forms a substitute for the normal element of consideration that is a part of every contract.

What happened with your security deposit? At the very least, this should be credited against what is owed. At the most your portion should be returned to you if the court finds you do not owe anything because the landlord should have let you know that the other tenant had stopped paying.