Lake Biwa Marathon
In 2018 he took first place at the Houston Half Marathon with a time of 1:00:01. On 4 March 2018 Robertson came third in the Lake Biwa Marathon, in a time of 2:08:26, breaking Rod Dixon's New Zealand record by 33 seconds. Four weeks later, Roberson defended his Crescent City Classic 10 km title in 27:28, equalling his brother Zane's national record.