(los Angeles County - Tenant Legal Advice) New Property Manager Says My 30-day Notice Isn't Valid Because Roommate Isn't Leaving With Me. We Have No Written Lease Agreement.

Location: Redondo Beach, CA.

A little context: I rent with a roommate in a fully covered unit. For many years, my only lease agreement for the property was a month-to-month sublease to [roommate]. This changed in 2023 when 1.) the landlord died, and 2.) [roommate]’s COVID protections expired, and [landlord]’s wife and daughter immediately went after [roommate] for $10k+ in unpaid rent. I saved [roommate]’s ass by begging the wife + daughter to reconsider their unlawful detainer suit and agreeing (without signing a formal lease) to pay my portion of rent directly to them from then on. They dropped the unlawful detainer, [roommate] has squatted ever since.

Fast forward to now: The landlord’s wife + daughter sold the house in Dec 2025 to a giant property investment firm. I haven’t signed anything, but I now pay rent to a property management firm. [property management firm] posted notice immediately after the property closed, 12/30, leaving me two days to figure things out before rent was due. Their first invoice for rent was for the total house amount, addressed to [roommate]. I scrambled & got them to put my name on the invoice instead of [roommate]’s, and paid the full amount myself to avoid an at-fault eviction.

I tried multiple times to get [property management firm] to separate my and [roommate]’s invoices to reflect the split we had with the last owner, but got nowhere with them. I can’t afford to keep paying 2 people’s rent for this place, so I mailed [property management firm] a 30-day notice and lined up an apartment nearby with a 3/1 move-in date. But last night I get an email from a regional manager, saying that [property management firm] can’t “formally process” my 30 day notice and “move forward” with my move-out without “confirmation from all named leaseholders on the lease.” I have not signed any kind of lease with [property management firm] and neither has [roommate], but I guess I’ve entered an implicit agreement just by paying rent and getting the invoices to be made out in my name instead of [roommate]’s. My roommate hasn't paid them a cent, though, so as far as I can tell he's a tenant but not a leaseholder?

Do they have the legal right to keep me from moving out (or to come after me for rent if I do it anyway)? How on earth should I respond to this?

TL;DR: I rent with a roommate in LA County. Roommate is a squatter, I've been paying 100% of rent. I want to move out, and mailed in my 30 days' notice, but property manager is saying the notice is invalid, despite me and roommate never jointly signing a lease, and neither of us holding any kind of written lease agreement with the current landlord.

Any advice would be hugely appreciated. If you are knowledgeable and willing to give me a few minutes of your time, I would happily return the favor by leaving a positive review of your practice, comments on your socials, etc. I am at my wit's end here.