Could Roxas have done it?

[Tatsu]

Xion told Roxas near the end to stop Xemnas. Of course Roxas ends up getting captured before trying. But do you think he could've done it? If Roxas had not been captured and fused with Sora do you think he could've stopped Xemnas on his own?

[Du Soleil.]

Nomura said that Roxas would essentially be more powerful than Xemnas, IIRC. Having discovered what Xemnas really wanted to do with him, I'd say that yeah, Roxas would have the motivation to stop Xemnas and probably could. However, he'd know, I think, that as Sora, he's more complete and more powerful. So, take from that what you will.