Rollin Hand was a member of the I.M.F force and was called upon to do missions by Dan Briggs and Jim Phelps.He was played by Martin Landau, who was already somewhat famous before accepting the role of Rollin. Notably he turned down the opportunity to play Spock on Star Trek, which Leonard Nimoy later filled. Martin Landau and his wife Barbara Bain left the show after Season 3 and Leonard Nimoy took his place as Paris, who filled basically the same category as Rollin.
It is unknown if Rollin retired, was transferred to another section of the Government or if he remained with the I.M.F doing missions with some other I.M.F members. Hand was a magician, actor and master of disguise and that is likely how he was discovered by the I.M.F.