Greetings, Gary, and welcome. You asked:

<<I am wrestling with the decision to preserve my options by converting an existing regular IRA to Roth. The regular IRA includes both taxed and untaxed contributions. In addition, I am a federal civil servant with the Government's equivalent of a 401K (referred to as Thrift Savings Plan) This vehicle has limited investment options consisting of an S&P500 index fund, bond fund or money market fund.

My original longstanding plan upon retirement was to rollover the proceeds from the Government 401K into my regular IRA to provide greater flexibility of investment options including investment in individual equities. My research indicates that if I convert to a Roth, that a rollover of the Thrift Savings Plan funds would NOT be permitted. If I decide that the Roth conversion makes sense can an additional regular IRA be established to receive the proceeds of a rollover from my Government plan?>>

As Chris aka SnootFool mentioned, you cannot roll retirement plan money directly to a Roth IRA. It must first go to a traditional IRA, and once there it can be further transferred to a Roth IRA. To accomplish that when the time comes, you may use an existing IRA or a new one. Any broker/fund can help you with the process should you wish to use a new IRA for that purpose.

Regards….Pixy