SilentDawn’s review published on Letterboxd:
Room begins and ends with two tremendous, tender performances and one evolving relationship. Nothing else matters when the camera focuses on them, mainly because Brie Larson and Jacob Tremblay fill every space, whether large or small, with the same loving affection for the story they're telling and a continuous, truthful intimacy.
The issues with Room, are basically, everything else. Lenny Abrahamson's direction fits at first but he soon tries to tell a calculated style of evolution visually, and it doesn't work. In general, the second half, as gentle and gradually moving as it is, feels wonky and disjointed. Also disappointing is the score by Stephen Rennicks, which flourishes through predictable beats, rising to the role of sappiness when the direction decides to go for a more deliberate approach.
In a film with lesser roles in front of the camera, these issues would've collapsed the entire foundation that Abrahamson created in the first half. However, these aren't "lesser" roles but bold and softhearted achievements. Room isn't just saved by its performances, It IS these performances, and sometimes that's enough.