How do Holden and Phoebe reverse roles at the end of the novel?
Throughout the novel, Holden expresses his desire to run away from everything. He can't stand all of the phonies that are around him. He can't figure out a way to interact in a positive way with just about anybody. He can't stand the two teachers that he interacts with. He's simply fed up with everything. He tries to convince Sally to run away with him, but she flatly refuses. As a last ditch cry for attention, Holden writes Phoebe a letter that explains his plans to leave and run away.
Amazingly, Phoebe meets Holden at the museum with a suitcase of her own. She plans to run away with Holden.
She put the suitcase down. "My clothes," she said. "I'm going with you. Can I? Okay?"
That causes Holden to get upset, and then he refuses to run away. That's the role reversal. Holden wants to now stay while Phoebe wants to go. Holden becomes the voice of reason and Phoebe is the person acting emotionally and impulsively.
"Did you mean it what you said? You really aren't going away anywhere? Are you really going home afterwards?" she asked me.
"Yeah," I said. I meant it, too. I wasn't lying to her. I really did go home afterwards.