Here's some more reading on the process: How to Evict A Roommate in California.And here's a scenario on point with an answer from an attorney:https://www.avvo.com/legal-answers/i-live-in-ca-and-need-to-evict-my-verbally-abusive-1632504.html

I  can only rent to 3 unrelated roommates  in one house but HUD would say 9 related people can live there....go figure.One thing in a two bedroom to limit vehicles. 

. 😄 I haven't even listed the new home yet because we want to do some work on it and I've already got people wanting to rent it (college kids and single people wanting roommate situation, they approached the seller and he gave them our contact info) - 1/2 the square footage and no upscale features, but it is a lovely historic home in downtown area.

She can get a roommate.

They have not been paid on, and 4 are medical accounts, 1 library fine, and an electric company.The application has a clause for reasons for denial, but there isn't anything in the signed lease other than a section that subletters or roommates must go through the application process and be approved. 

For some reason, it's like having a roommate you didn't pick out.  

Consult an attorney and proceed with eviction and stop this musical roommate nonsense.

First place has now been awarded to the three room mates who despite the listing showing clear DQ's, and several emails where I reminded the lady who contacted me about the DQ's, show up anyway and tell me that the one room mate (I had no idea there were going to be room mates, like I said, she never mentioned it even after I brought it up in the emails as a DQ..) has his own house.

It would be easier to find roommates as tenants.And by the way, I bet you could get a full kitchen in the tiny studio.  

We marketed to grad students who didn't want roommates, and single working people who preferred to save money than pay for a fancy apartment.We had ancient small oven/stoves - but they were all detailed before each tenant, so were super clean.