A lock and loose forward, Robertsen was capped nine times for the national team, debuting against the Wallabies at the Sydney Cricket Ground on Canada's 1985 tour of Australia. He made the Canada squad for the 1987 Rugby World Cup but injured his knee in a practice match and had to spend the tournament on the sidelines. In 1991, Robertsen made his second World Cup squad and played in two of Canada's pool fixtures, against Fiji and France. A back injury suffered in the France match kept him out of the quarter-final against the All Blacks, which Canada lost 13–29.[3][4]