Ninja: Walk in shadow.

[dday3six]

You're forgetting that every Job requires lv30 in one class (in this case, Rogue) and lv15 in another class (most likely pugilist or lancer), which is also one of the two classes they'll get cross-class abilities from.

It's not outside the realm of possibility for the secondary class to be Thaumaturge or even Arcanist. There is precedent with Paladin and Conjurer.

If SE followed the model of a job's secondary being in a different city-state, assuming the Rogue is in Limsa that would point to Thaumaturge. However that was likely a design element meant to encourage exploration, so is possible SE might break away from that trend as well.