Keith Garrett’s review published on Letterboxd:
I may have cried most when Jack said "I love you grandma" after she cuts his hair, but I felt the most crushing sadness when he said wanted to go back to bed "in room" the day after they escaped.
As a viewer, watching this film, you feel this claustrophobia when they're still in room. I could not shake the feeling that I would go absolutely insane if locked in there, and I naively expected Jack to feel nothing but excited (maybe a little scared) to see the real world. But that's where the complexities of the situation come to the forefront. Room is all he's ever known, thinking that "space" is right on the other side of the door, not the backyard of a monster. Everything he's been told is suddenly being proven false, by the very source who told him these things in the first place, to protect his sanity.
So when he expresses a desire to go back, Joy - and the viewer - feels a devastatingly complex well of emotions. Room was a prison, but to him it was Home.
Jacob Tremblay, as you might have guessed, broke my stone heart and exhibited a surprising amount of understanding of his character's complex mindset. And Brie Larson is right there with him, knocking it out of the park with an understated performance that's never showy or begging for an Oscar (cough Leo cough) which is exactly what makes her deserving of one.