Sounds like we are missing some information possibly? I'm not really understanding why he essentially wants to allow your roommate to live there without being on the lease but is willing to put them on a new lease in April...im guessing your original lease ends in April and the lease you are signing now is am updated lease? Are you actually signing a whole new lease or it is an add/drop addendum? It just seems wierd that he wants to sign a lease now and then again in April.

When I was a PM I used to say we protected landlords from themselves because they are often spiteful and clueless. That said, fair housing laws don't prevent someone from inquiring if a tenant will require an accommodation (like a support animal). That said, he shouldn't be asking you about it...he should be vetting the new roommate just like he hopefully did for you and adding them to the lease. Your roommate's information is private and even you should not be discussing it.

I'm not seeing anything discriminatory here necessarily. He just sounds like a dumbass.