When do I have to withdraw money from a Roth?

You don't. While traditional IRAs require that you take minimum withdrawals starting at age 70 ½, Roths have no mandatory withdrawal requirements. So if you retire and you have other assets to live off of, you can leave the money in your Roth and allow it to continue to grow for as long as you like. That's a terrific advantage Roths have over traditional IRAs.