Though not initially elected in the 1994 general election,[2] Robertsen joined the National Assembly in 1995, filling a casual vacancy.[3] In the 1999 general election, he stood for election as a candidate for the opposition New National Party (NNP), but he was ranked seventh on the NNP's party list for the Eastern Cape and did not gain a seat.[1] In the next general election in 2004, he returned to the ANC, which elected him to one of its seats in the Eastern Cape caucus of the National Council of Provinces.[4] He served a single term there.