I'm pretty sure Roy already knows it's Tarquin, or at least suspects it. He knows that not-thog is:

1. A human male

2. Meele focused

3. High enough level to fight off the entire order

If he didn't know before, he'll know it now.

And as for Nale, I predict that he'll be in a bodybag before this arc is done. There's one gate left, and the side-villains are going to be dying like flies to make way for the final battle.