The "Academy Lt." who was her instructor in Advanced Tactical Training was never formally identified as Chakotay. This was the original idea, but they decided against it on Voyager when dealing with Chakotay's backstory. The actual name of the instructor was never mentioned on screen. Chakotay's stated date of resignation on Voyager is a couple of years before Ro would have been at the Academy, anyway
They actually do --- Episode: "Preemptive Strike" right at the 8:47 mark on my video they mention "Lt Cmdr Chakotay" where Ro goes on to say "A man I both respect and admire...".
It actually would have been a very powerful opening to have Ro on Voyager if Michelle Forbes could be goated into settling, although what position she'd actually play is a bit of puzzle work. Ro Laren as Chief of Security would have probably been far more entertaining then Tuvok, but then again, we don't need Ro Laren and B'Elanna on the same ship; I don't think the structural integrity of the ship would hold >.<