Following his senior year, Rooney signed a professional contract with the Albany Devils of the American Hockey League.

[3] Beyond his father, Rooney's cousins Joe and Chris played NCAA college ice hockey while his uncle Steve won a Stanley Cup with the Montreal Canadiens.

In his final year with the Berkshire Bears, he helped them defeat St. Sebastian's in overtime to claim the 2012 NEPSAC Martin/Earl tournament championship title.

[4] Over his two years at Berkshire, Rooney totalled 58 points and earned MVP honors in the Large School playoffs.

[2] He scored his first collegiate goal during the Friars Hockey East Semifinals loss to the UMass-Lowell River Hawks on March 22, 2014.

[7] In this new role, he helped the Friars qualify for the Hockey East Semifinals against the fourth-seeded New Hampshire Wildcats and scored the team's only goal in their 3–1 loss.

[1] At the conclusion of his sophomore season, Rooney was invited to participate in the New York Rangers Development Camp as a free agent.

As a result of their lacklustre start to the season, the Friars only qualified for the 2015 NCAA tournament after Minnesota beat Michigan in the Big Ten Championship.

[18] On March 29, 2016, Rooney concluded his senior year at Providence by signing an amateur try-out agreement with the Albany Devils of the American Hockey League (AHL).

[33] While the Devils were competing in the 2018 Stanley Cup playoffs, Rooney was one of seven players from Binghamton recalled as support for their first-round series.

[33] While he was originally returned to the AHL to start the 2018–19 season, Rooney was recalled back to the NHL on October 20 and played in four games.

[42] As the Devils continued to struggle to win games, head coach John Hynes and general manager Ray Shero were both fired.

At the time of Shero's firing in January, the Devils had maintained a losing 17–21–7 record and were last place in the Metropolitan Division.

Interim head coach Alain Nasreddine praised the chemistry between Rooney and John Hayden on the fourth line as part of the reason for the team's success.

[45] After four seasons within the Devils organization, Rooney left as a free agent to sign a two-year, $1.5 million contract with the New York Rangers on October 9, 2020.

[50] Part of this reason was because after playing in his 200th career NHL game on March 2 against the St. Louis Blues,[51] Rooney was placed on injured reserve and listed as 'week-to-week'.

[52] He missed 15 games before returning to the Rangers lineup on April 9 and helped them clinch a spot in the 2022 Stanley Cup playoffs.

[56] On July 13, 2022, Rooney left the Rangers as a free agent and signed a two-year $2.6 million contract with the Calgary Flames.

[58] Rooney made an immediate impact with the Wranglers once joining the team, scoring an assist in his season debut against the San Diego Gulls.

[62] Throughout most of the regular season ansd the playoffs, Rooney often played on a veteran line with Brett Sutter and Clark Bishop.