I am currently on a years lease that goes until August, but am planning to move out in January. My roommates still have not found someone to replace me on the lease, and I have since been unable to find someone myself. My landlord is not agreeing to let me off the lease. Is there anything else I can do to move out if no one replaces me on the lease and not be liable to pay rent still?

No. A lease is a contract. You signed the lease and agreed to live there until August. You are therefore responsible for your share of the rent until a replacement can be found.

Try Craigslist

They have covered it fairly well, you are obligated to pay the rent till the end of the written lease. If they or if you find someone to move in, that can release you.

But until then you owe the rent