Career
He lives in Addis Ababa, Ethiopia. He competed in the 2013 World Championships in Moscow over the 5000m, where he finished 14th in a time of 13:46.55. At the 2014 IAAF World Indoor Championships, Robertson finished 12th in the final of the 3000 metres event a in a time of 8:01.81 after running a New Zealand National Indoor Record of 7:44.16 in the heats.
In 2015, Robertson set a New Zealand and Oceanian record in the half marathon with a time of 59:47 at Marugame.