If you are serious about quarantining, you can buy a used dog kennel on CL pretty inexpensively. Tie a tarp over the top for shade and to keep the rain off, and a rooster could live comfortably in that for a couple of weeks at this time of year.
I use dog kennels, the welded ones, not the chain link, for my night runs. I've got stock panels over the top to keep critters out.
I've also got another kennel set up with shade cloth over it for raising my plants that can't take full sun. That's to keep the bunnies out, but it is secure and that is my quarantine house.
Of course with ducks, I can put my plants up on tables and ducks don't fly.
A kennel is a one time purchase and good forever. I seem to find a lot of uses for my kennel panels. I had kennel panels across the roll-up garage door so I could reduce the heat in the garage where I've got my brooder. It got blast furnace hot in there this summer if the door was closed. With the door open, the predators could have gotten in to eat my ducklings. A couple of panels solved that issue.