Roth IRA is not guaranteed earnings. It can go up or down.
breh that goes for any investment. The smart thing is to have it in funds that track the market like the S&P. On average you get around 7-12% annually, beating inflation by a significant margin. As long as you keep contributing and keep expense ratios low, you will earn money.
And w/a Roth IRA again it's like a super savings account. You have access to your contributions at any time without penalty, while the earnings grow tax free. Best case scenario is to not touch the Roth IRA at all, but if you must, it's a super savings account that earns money tax free.