"....Gryffindor’s newest member of the Quidditch team - our - your superb new Chaser - Rose Granger-Weasley".
-- Professor McGonagall (CC1.4)
It is announced by Headteacher Minerva McGonagall that the new Chaser for the Gryffindor Quidditch Team is Rose Granger-Weasley. She has to try not to show her partiality to Gryffindor by refraining from praising Rose too much (CC1.4).
Scorpius Malfoy applauds Rose’s appointment, although Albus questions why he is cheering for the wrong team – but Scorpius likes Rose (CC1.4).
Her mother Hermione Granger, before Rose’s first year at Hogwarts, had said that Rose was worried whether she would break the Chaser scoring record in her first or second year (CC1.2). It seems that the exception made for Harry Potter to join the Quidditch team in his first year (PS9) wasn’t allowed again for allow Rose to be able join the team before now.
Quidditch tryouts take place at the start of the school year.
From the Web
Pottermore: Harry Potter and the Cursed Child
The theatre production opened in the West End of London at the Palace Theatre on 30 July 2016, with Cherrelle Skeete in the role of Rose Granger-Weasley and Sandy McDade in the role of Minerva McGonagall: Harry Potter and the Cursed Child, Parts One and Two