He served in the Legislative Assembly of Manitoba from 1945 to 1958, and was the Minister for Agriculture in the government of Douglas Campbell.
[citation needed] Robertson enlisted with the Royal Canadian Air Force in 1940, and was discharged in September 1945 with the rank of Flight Lieutenant.
On November 7, 1952, Robertson was appointed Minister of Agriculture in Douglas Campbell's government.
He was easily returned in the 1953 election, and was appointed Minister of Public Works on July 6, 1956.
[1] The Liberal-Progressives were defeated in the 1958 election, and Robertson lost his own legislative seat in the redistributed constituency of Swan River,[1] finishing third against Progressive Conservative candidate Albert H.C. Corbett.