A participant is still working with the company and has not met the age requirmenmt for an in service distribution.

They want to Rollover their account from the 401k into a Roth IRA , becauase they think Roth IRA offers better investment selections.

Is this Allowed?

I think you anwers your own question --

A participant is still working with the company and has not met the age requirmenmt for an in service distribution.

I agree, but the participant agrees those are the rules for a traditional 401k but with the roth it is different due to it being after tax dollars…

Any help here?

Roth-401(k) are still 401(k) and subject to the same withdrawal restrictions as traditional-401(k). The only difference is the taxation on distribution.

Any money in the plan whether it be pre-tax, roth, match, profit sharing, rollover, etc. is subject to the rules of the plan. The Summary Plan Description will address when in-service distributions are allowed.