* The main disadvantage of a Roth IRA (when compared to a traditional IRA) is that contributions are not tax-deductible. If one contributes $1000 to a traditional IRA while in a high tax bracket, one can often receive a tax deduction, substantially reducing the initial cost of contributing (or, potentially, allowing someone without much disposable income to shelter more income). This is not the case for the Roth IRA. It should be noted that the money in a traditional IRA is taxed once it is withdrawn at retirement. If one is not able to max out one's IRA contributions, and ends up in a lower income tax bracket at retirement, then one will wind up with less usable cash by choosing a Roth IRA over a Traditional IRA.
* With a Roth IRA, there are heavy penalties for early withdrawals of earnings (withdrawals up to the total of contributions + conversions are tax-free). An unqualified withdrawal of earnings will result in federal income tax plus a ten-percent penalty on the amount. Fortunately there are many exceptions, such as buying a first home and paying qualified educational expenses.
* There is also the risk that Congress over the next few decades may decide to tax earnings on Roth IRAs.
* The perceived tax benefit may never be realized, i.e., one might not live to retirement or much beyond, in which case, the tax structure of a Roth only serves to reduce an estate that may not have been subject to tax. One must live until their Roth IRA contributions have been withdrawn and exhausted to fully realize the tax benefit. Whereas, with a traditional IRA, tax might never be collected at all, i.e., if one dies prior to retirement with an estate below the tax threshold, or goes into retirement with income below the tax threshold.