I'm not as well versed on the options at retirement, because I'm not close to it yet. So maybe someone more up to speed on the options there can give some input.

I believe that at retirement (and only a few very limited situations prior to that point), you can roll everything in your 401(k) to an IRA. Trad or Roth, with the associated tax implications for any conversions performed. As far as I know, there is no way to move company dollars or your own money put in as 401(k) dollars out of the plan prior to retirement.

If, however, you select to have your own money put in as After-Tax 401(a) contributions, then you can roll those dollars out of the plan via an in-service withdrawal to a Roth IRA. This is the Mega-Back-Door Roth IRA contribution, which you can google for more info.