Dear New York Tenant:
New York State law prohibits a landlord interfering with a tenant's right to a roommate. Period. The statute provides a legal remedy for a tenant suffering a landlord messing with the legal right to a roommate.
The answer provided to you is in the nature of general information. The general proposition being that you should try to avoid a bad outcome if you can.
Your current lease should dictate the terms of your ability to have a roommate. The condition of the property / bedbugs are a separate and distinct issue from an additional tenant. You should consult a landlord tenant attorney to determine your rights and if your apartment is inhabitable.
I agree with Mr. Smollens, but want to point out - because there always seems to be confusion in this area - that it's of no consequence that you call him your roommate if you are collecting rent. Collecting rent makes him a tenant and then you do not have the absolute right to sublet absent an agreement (like the lease with your landlord). So, be careful.
I may be guessing or not licensed in your state. No atty/client relationship exists. I earn my living collecting points for "helpful" answers.