If you are under age 59-1/2, you will pay the regular income tax on the conversion, and a 10% penalty for early withdrawal. If you also withdraw earnings (increase in value in the Roth) that is also subject to regular income tax plus a 10% penalty.
If you are over age 59-1/2, you pay income tax on the conversion per the normal rules, but you don't pay an additional penalty for early withdrawal. If you withdraw earnings, and the Roth IRA has been open less than 5 years, the earnings are taxable (but without the 10% penalty).
