He was born in New Perth, Prince Edward Island, as the son of Peter Robertson and Annie McFarlane.

During his tenure, he served as a Minister Without Portfolio in the cabinets of Robert Poore Haythorne and Louis Henry Davies.

While several Canadian provinces did at the time allow people to simultaneously hold seats in both the provincial and federal legislatures, Prince Edward Island had enacted a law explicitly disallowing this.

The federal committee adjudicating the matter was dominated by the governing Conservative Party, whereas Robertson was a Liberal.

In 1902, he was appointed to the Senate of Canada by Wilfrid Laurier, representing the senatorial division of Prince Edward Island.