Well do prepare a crate to put the roosters in. I don't think a 6 foot fence will work for long.
What a wreck. I do think it is good That you did communicate with your landlord before this happens.
https://104homestead.com/quarantine/
Mrs K
Truthfully I would not bother adding the buffer zone if it is only going to be a few feet. Your birds have already shared air space, for quarantine you need at least 36 feet between the birds.
The sight blocking cloth might help, won't hurt, but roosters are going to want hens, is your run...