FA chairman Greg Dyke confirmed the additions yesterday.
Dyke said: "Rio's vast experience as a player developed through West Ham's successful youth system, winning Premier League and European titles with Manchester United and representing England at World Cups means he has a huge amount to offer to the debate.
"We have been speaking to Rio and Manchester United for some time about him joining the group - before we named the other members of the commission.
"However, as he is a current Manchester United player we needed to be sure that Rio had the necessary time to fully participate on the Commission and not impact on his day job. It has been agreed he does.
"As a current player with forthright views and opinions on the game, we can look forward to Rio providing significant insight and experience."
Dyke added: "It is important Roy can offer his views as the current manager of the national team and share the knowledge he has gained when working for many years in a number of countries. I wanted the international fixtures to be completed before announcing this to avoid any distractions for Roy at such an important time."
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