He may have been killed along with other members of the DHARMA Initiative in the Purge, or he may have left the island sometime between 1977 and The Purge.
In the Sky1 special"Lost: Season 5 Revealed", Iain Lee, the presenter of "The Lost Initiative" podcast. When Lee was visiting the filming site of "Namaste", he asked director Jack Bender to give him a background role. After Bender's approval, Lee wore Jerome's jumpsuit, and interviewed the cast. However, Lee later believed the name Jerome didn't match him, so he decided to wear the Ronnie's jumpsuit, and filmed a scene as a background character, but the scene never made it to the final cut.