There is no provision in the tax law that would allow anyone to convert taxable funds and treat it as a tax-free transaction, regardless of how long the assets have been rolled to the Traditional IRA. Of course, conversions of nontaxable amounts are not taxable.
A Roth conversion can always be reversed through recharacterization, thereby making the conversion null and void, but all that can be avoided by ensuring that the individual is aware of the tax implications of the conversion.
For more insight, see Did Your Roth IRA Conversion Pass Or Fail?
This question was answered by Denise Appleby