Continuing his hockey career, Roberts joined the Vancouver Millionaires where he was named a PCHA all-star at left wing and led the league in scoring with 43 goals in 1916–17.

[3] When he turned professional in 1909 by joining the Ottawa Hockey Club, Roberts was one of the youngest players in his league at the age of 18 years.

[3] Roberts found it difficult to both study and play hockey, but praised the support of his classmates and the faculty in helping him earn his degree.

[10] He retired in 1918 to focus on his medical career in the Howe Sound region of British Columbia,[4] but was lured back to the PCHA by the Millionaires for the 1919–20 season.

[12] Roberts was sometimes described as being the inventor of the "curved shot", preceding and outmatching players such as Harry Cameron, Babe Dye and Didier Pitre.

[8] Bernie Morris, and Hall of Famers Frank Foyston and Lester Patrick all attested to the unrivalled effectiveness and dramatic trajectory of Roberts’ shot.

[13] Clint Benedict, often considered the greatest goalie of the 1893–1926 era[14] also gave praise to Roberts’ accuracy coupled with his ability to curve the puck.

[15] Roberts was noted for being able to get his shot off at very bad angles from close in, as well as drive it in from far outside the reach and typical positional range of defenceman.

[16] Despite being a physical player, Roberts (like his contemporary Frank Nighbor) was noted for his gentlemanly conduct on the ice – which he may have used to protect himself from retaliation.

The Ottawa Senators, then of the National Hockey League, attempted to bring him out of retirement again and Cornell University sought his services as a lacrosse coach.

Roberts turned down both offers and chose to retain focus on his medical career; He moved to California where he taught for a time at Stanford University Hospital.