Because a Roth IRA is significantly different from a traditional IRA, the best Roth IRA investments are also very different. Traditional IRAs offer limited options for investing, for saving, and for how you use the money in your IRA.
The Roth IRA is for people who choose to have their investment pre-taxed in hopes that their tax bracket will rise, not lower, after retirement. This kind of IRA also requires the desire to take aggressive risks.