See answer here - https://ttlc.intuit.com/community/retirement/discussion/can-i-recharacterize-my-roth-401k-contributi...
You can only recharactorize a Roth conversion from a Traditional IRA back to a Traditional IRA. (Rechactorized means putting it back to where it came from).
You cannot convert a Roth IRA to a Traditional IRA which is this would be since the Roth is not a conversion but a rollover from an existing 401(k) Roth. Since a Roth is after-tax money, converting it to before-tax money cannot be done and is not allowed.
(Note that after Dec 31, 2017 Roth recharacterizations can no longer be done under the new tax law).
