Gatsby has his own room under normal circumstances because he really hates other cats. He full-out attacks them. So my home office doubles as Gatsby's house. Because I spend 8-10 hours a day in there working, it's easy to keep a close eye on him.

If he needs closer confinement for awhile, my sister has a good sized dog crate I can borrow. That might be necessary to keep him from trying to jump onto my desk or his cat tree.