I do both...I bought some physical Rhodium bullion 2 years ago from www.bullionexchanges.com and unfortunately I paid in BTC...lol but hey, who knew? I also bought a composite ETF (Platinum & Palladium) from Sprott using my IRA...so if you want to play the paper game, that is available too. Its not Rhodium, but for the most part, the same factors are in play.

http://www.sprott.com/investment-strategies/physical-bullion-trusts/#