Due to his contribution to the set-up of the statue of Birushana Buddha at Todai-ji Temple, Roben was appointed as Shosozu (junior secondary prelate) in 751 and promoted to Daisozu (the upper Buddhist priests in the second highest position) in 756 while Ganzin was also appointed as Daisozu in that time.
後に東大寺盧舎那仏像建立の功績により、天平勝宝3年(751年)　に少僧都となり、天平勝宝8歳(756年)には鑑真とともに大僧都に任じられる。