AFFC, Jaime I, page 172:
So there you have it. The three prisoners that Longwaters is referring to are obviously Rorge, Biter and Jaqen. And since Ned signed them over to the Night's Watch before he was arrested, that means Jaqen was already a prisoner before Syrio's confrontation with Meryn Trant. So they cannot possibly be the same person.
It's always great to find these little gems in the text.