ROG is THF - Yoshi stated this outright (and the game's storyline even mentions it in a joking way, that the ROG's Guild was called 'The Upright Thieves', but changed their name to avoid the negative connotations with the word, which is why the class is also known as ROG instead of THF meta wise - Yoshi simply felt having a Warrior of Light as a 'thief' stretched credibility too far. And yes, I know it's a reoccuring Job in the series, I'm just pointing out the feelings of the game's producer and director, the one who creates this game.).

So we already have got THF under a different name, but it's basically the same thing.