Ronan made his professional debut as a defenceman with the Pittsburgh Bankers of the Western Pennsylvania Hockey League in 1908–09, then would break his contract to leave to play with the Toronto Professionals, finishing with a few games for the Haileybury team in the Temiskaming Professional Hockey League. He would stay with Haileybury in 1910 in the inaugural season of the NHA. In 1911, Ronan remained in the NHA after Haileybury returned to the TPHL, as a member of the Renfrew Creamery Kings in their final season in the NHA. For the 1911–12 season, Renfrew dropped out of the league and its players were dispersed to the remaining clubs in the league by drawing lots. Ottawa picked Ronan after the Wanderers had picked Cyclone Taylor, and tried to trade Ronan to the Wanderers for Taylor without success. Ottawa's regular centre Marty Walsh was not playing well and Ottawa tried Ronan out at centre. Ronan blossomed at centre, scoring eight goals in one game and five in another, ending up with 35 goals in 18 games. While a member of the Senators during the 1911–12 and 1912–13 seasons Ronan was also a member of the NHA Eastern All-Stars, managed and coached by Art Ross, who played series of exhibition games against an All-Star aggregation from the Pacific Coast Hockey Association, scoring a total amount of 8 goals in 9 games over two years. Ronan would play two more seasons with Ottawa before being sold to the Toronto Shamrocks before the 1914–15 season, but did not duplicate his goal totals. Ronan played a season and a half with the Shamrocks and the rivaling Toronto club Toronto Blueshirts before being dealt to the Montreal Canadiens, playing on their 1916 Stanley Cup-winning squad, scoring a goal in the deciding game 5 2-1 win over the Portland Rosebuds. While with the Canadiens Ronan assaulted former Blueshirts teammate Alf Skinner in a game between the two clubs on January 22, 1916 which had him arrested by police and taken to the Agnes Street station in Toronto, although he was later released on $200 bail. The incident went to trial and Ronan was acquitted of the charge on January 31 before Judge Winchester in Toronto, with Canadiens manager George Kennedy acting as a witness for the defense. After the 1915–16 season, Ronan signed up with the military where he served until 1918, while being affiliated with the Ottawa Munitions of the Ottawa City Senior Hockey League. He returned to professional hockey and was re-acquired by Ottawa in a trade with the Canadiens in exchange for Harry Hyland. However, he had lost his offensive skills and was released after eleven games without scoring any goals.
