2010-11: Philippe Desrosiers played for the College Antoine-Girouard Gaulois midget AAA team in Quebec and won a silver medal with Team Quebec in the 2011 Canada Winter Games. Sharing the goaltending with Philippe Cadorette, he was 10-9 with a 3.54 goals against and .885 save percentage. Desrosiers was 2-3 in the playoffs with a 2.45 goals against and .907 save percentage. Desrosiers played two games at the CWG and had a 3.71 goals against and .837 save percentage. He was selected by the Rimouski Oceanic in the second round (29th overall) of the 2011 QMJHL Entry Draft.
2011-12: Desrosiers made his QMJHL debut, playing in three games for Rimouski, and played midget AAA hockey for College Antoine-Girouard. He was 1-2 in his brief stint with the Oceanic and had a 3.48 goals against and .899 save percentage. In 23 games for College Antoine-Girouard he was 16-4 with a 2.77 goals against and .907 save percentage. The Gaulois reached the Quebec midget AAA semifinals and in 11 playoff games Desrosiers was 6-3 with a 2.58 goals against and .905 save percentage.
2012-13: Desrosiers played 43 games for Rimouski in his first QMJHL season and was in net for Canada’s gold medal team at the 2013 U18 World Junior Championship. He was 22-8-5 with a 3.07 goals against and .900 save percentage for the Oceanic. Rimouski finished second in the East Division. Desrosiers played four games in the Oceanic’s six game playoff series with Gatineau and was 2-2 with a 2.26 goals against and .892 save percentage. At the U18 WJC in Sochi he was 5-0, including a 33-save effort in the gold medal game win over the USA; finishing with a 0.80 goals against and .970 save percentage. Desrosiers was ranked seventh amongst North American goaltenders in Central Scouting’s final rankings prior to the 2013 NHL Draft.
2013-14: Desrosiers attended camp with the Stars before returning to Rimouski for his second QMJHL season. He had the league’s fourth-best goals against (2.65); appearing in 52 of 68 games for the Oceanic. Desrosiers was 31-14-7 with seven shutouts and had a .907 save percentage. In February he set a QMJHL record by not allowing a goal in 213:15 minutes. Rimouski finished second in the East Division and reached the second round in the playoffs. Desrosiers was 7-3 in the playoffs, including two shutouts, and had a 2.34 goals against and .917 save percentage. He signed a three-year entry-level contract with Dallas in April 2014.
Desrosiers is an aggressive, confident butterfly goaltender that has a surprising amount of athleticism and quickness. He can get out of his butterfly stance just as quickly as he can get into it. He anticipates the play well and challenges adeptly with advanced rebound control at his age. Desrosiers understands the concept of directing rebounds, actively makes saves rather than just blocking shots. He moves well in the crease, mainly because he doesn't give up his leverage to push across entirely. Desrosiers is an active player. High shots can be problematic for him and he still has some holes to fill in his game.
Desrosiers attended training camp with the Stars before being returned to Rimouski for the 2014-15 season. Now in his third QMJHL season he is once again handling the bulk of the goaltending on an Oceanic team that has had the league's best record for much of the season. Playing for a high-scoring team like Rimouski he has enjoyed a margin of error he may not enjoy at the next level. Desrosiers physical ability, size, and durability, however, suggest he can be an NHL starter one day.