Historically, most of the senior ministers at Scots' Church have been trained or served in the Church of Scotland, including Robertson, who first worked at Scots' as an assistant minister between 1991 and 1994. He returned to Scotland and was parish minister in Appin And Lismore, North Argyll (1995–2000), but was then called by the congregation of Scots' Church to come back to Melbourne and serve as senior minister from February 2001. Robertson served as moderator of the Presbyterian Church of Victoria (2008–09).