Credit to him and credit to the academy, because I think we have got a good player there." Henderson scored his first goal for Celtic on 26 March 2014, the second goal in Celtic's 5–1 win away at Partick Thistle which clinched the league title. His form throughout March saw him win the SPFL Young Player of the Month award for that month. Manager Neil Lennon commented "He's been absolutely excellent", and added that "His attitude to work is fantastic and there's certainly a willingness on his part to get better". Henderson made a couple of appearances in the first few weeks of season 2014–15; playing against KR Reykjavik in a Champions League qualifying match and then in a league match away against Inverness CT. However, he thereafter completely dropped out of new Celtic manager Ronny Deila's plans for several months. Henderson regained his place in the XI in early January and scored an excellent left-footed strike against Hamilton Academical on 17 January 2015. Henderson featured for Celtic in the first leg of their Europa League tie against Inter Milan, coming on as a substitute in the second half and providing the cross which led to John Guidetti's late equalising goal in a 3–3 draw. A month later he played in the final eight minutes of Celtic's 2–0 League Cup Final win over Dundee United. Henderson completed a short-term loan move to Norwegian club Rosenborg on 31 March 2015. Rosenborg manager Kåre Ingebrigtsen described Henderson as a "very exciting player" and that he had "huge potential". Henderson made his debut for his new club on 12 April when he came on as a second-half substitute during a 6–0 win over Haugesund. After making another substitute appearance in a league match against Strømsgodset, Henderson made his first starting appearance in Norway on 22 April in a Norwegian Cup tie away against lower league Vuku. The midfielder opened the scoring after 8 minutes with a right foot strike. It was his first goal for Rosenborg, and his side went on to win 3–0. On 25 April Henderson came off the bench, on his 19th birthday, against Viking to score twice within 10 minutes. Rosenborg subsequently won the game 4–1. After making a total of 13 appearances, he returned to Celtic at the end of June 2015. Henderson was positive about his time in Norway, stating "it was a great experience, playing in a different league and in a foreign country."