There are many games on Roblox that hire people. Some popular ones include
Soro’s, Serendipity’s Support Center, Kohaú Hibachi Restaurant, and Boba Cafe.
How do these games hire enough staff to keep the game going?
Marketing + payments of some sort. These games market their staff positions to many people who then apply for the positions. These are sometimes paid, sometimes not. For this though, your game should be decently good and decently popular. The best way to do this is by growing a pretty large discord community and having it active.