Don't be to down. DDD went and basically said "lol oh yeah KH2 was full of lies. Anything can grow a heart eventually". Meaning you'll likely see Roxas back. Though not sure what dues ex machina they'll use.
You know what you'd pick? That's admission to pervhood. xD Worst yet your pick is younger.
Sora needed the memories back. Between CoM, Namine, Days, Roxas and Xion Sora's memories was all spread out and out of whack. To get them all back what was scattered had to be put back. Unfortunately for Roxas that included himself.