If you signed the lease then it is valid. If you ask for a copy of the lease I suspect that your landlord will happily provide it to you.
You are obligated under the terms of the lease and if you refuse to pay the rent then your landlord can evict you.
You have an obligation to your landlord the issue between you and your roommate is not his concern and does not weaken his right to collect rent under the terms of the lease.
Donald at Robinson and Henry, PC at (303) 688-0944 or Reception@RobinsonandHenry.com. The above information is provided to you “AS IS,” does not constitute legal advice and we are not acting as your attorney. Because we do not have a full view of the facts in providing the above information we make no claims, promises or guarantees about the accuracy, completeness, or adequacy of the information contained in or linked to this web site and its associated sites. Legal advice must be tailored to the specific circumstances of each case and the information provided to you may not be an appropriate fit in your case. Nothing here is provided or should be used as a substitute for the advice of competent legal counsel. This postings is for educational and information purposes only, not legal advice or legal opinions. The information is not intended to create a lawyer-client relationship between the author and you.
If the landlord has a copy of the lease with your signature on it then it is valid against you. What the landlord can do is to sue you for payment of rent from the beginning of this month until either the property is rerented or the 12 month period ends. You cannot simply walk away from a lease in the middle without the landlord's agreement and without consequence.
You can reach Harkess & Salter LLC at (303) 531-5380 or info@Harkess-Salter.com. Stephen Harkess is an attorney licensed in the state and federal courts of Colorado. This answer is for general information only and does not create an attorney client relationship between Stephen Harkess or Harkess & Salter LLC and any person. You should schedule a consultation with an attorney to discuss the specifics of your legal issues.