Is it possible that after the roof coming off our apartment building and having flooding we can break the lease by one month?

Yes, it is certainly possible, but an attorney would need to review the terms of your lease, and specific facts surrounding this situation in order to give you a definitive answer. In addition, local laws may have an impact on the manner in which proper notice is to be given to your landlord. Therefore, I would recommend organizing your lease and all other information you have relevant to this situation (i.e. pictures and communications with your landlord) and consulting with a landlord tenant attorney individually for a consultation.

The short answer is, "probably". It depends on the actual facts of the case. If your apartment was wiped out by fire the landlord would have no more apartment to rent to you and that would effectively end your lease. In your case there is still an apartment but you say it is water damaged. If the water damage is so severe as to make the apartment uninhabitable then the landlord has no apartment to rent and the lease should end. Much also depends on the terms of your lease and what it says about this eventuality. You should ought to have an attorney review your situation and lease and, if you plan to terminate early, write the termination letter.