A Kryptonian exiled in space by Jor-El after he impersonated his brother Nim-El in order to steal ultra-powerful weapons. Escaping his punishment, Roz-Em travels to the time of Superboy and persuades Clark and the Kents that he is actually a Superman version of Superboy formed during a freak Red Kryptonite accident.
Convinced that two versions of himself can not exist on Earth, Superboy sadly agrees to leave the planet forever, however Jonathan Kent finally realizes the hoax and sends Krypto to retrieve the Boy of Steel. Roz-Em is dispatched to the Phantom Zone for all of his crimes of impersonation (Adv No. 304/1, Jan 1963: "The War Between Superboy and Superman!").