If you have money in a traditional pre-tax IRA, someone always pays the income tax.
You pay the tax if you withdraw the money. You must withdraw at least something once you turn age 72 (RMD). Even if you die and your children or spouse inherit the IRA, they must pay income tax on any money they withdraw. (IRA's are an exception to the stepped up basis rule for inheritance.)
The only thing you can do is change when you pay and what rate you pay. For example if you withdraw less than $12,000 per year and have no other taxable income, you won't pay tax because it's less than the standard deduction. If you withdraw up to $40,000, you'll pay 12% income tax, and more than that, you'll pay 22% income tax. (Those numbers are for single. Roughly double them if you are married.). If you withdraw in a year that you have income from work, you will pay a higher percentage than if you withdraw in a year when you don't have other income. And so on.
A Roth conversion means you convert some or all of your traditional IRA to a Roth IRA. You pay income tax on the converted amount, but you don't have to pay tax in the future, since Roth IRA withdrawals are tax-free. But this is tricky. Depending on your current income, you might pay more tax now to convert to a Roth than if you withdrew the money from a regular IRA after you retired. A financial planner can help you understand your options.
