Roth IRAs are excellent tools for FIRE, as listed above. If you plan to use ACA subsidies for healthcare, you will also need to have some income each year (otherwise, you will be on Medicaid). This can be achieved by having savings in taxable (dividends and capital gains will count as income, even if you are under the limit for them to be taxed) or by converting from traditional 401k/IRA to Roth. These will be taxed at your ordinary income rate. As stated by a previous poster, these conversions can be withdrawn tax and penalty free after 5 years.