Drouin wasn't predestined to be a headcase, that's the whole point. Having Drouin go back to juniors no doubt contributed to his issues both in terms of his relationship and the headcase label and it led to reinforcing non-pro habits in his game that he still has. It's easy to say oh he's just a bust, but it's simplistic and wrong. The environment a player is in has a huge impact on how well they will develop, being rushed to the pros and being overmatched is bad, but so is playing at a level where you aren't being properly challenged.
Time will tell whether Roy's development also is hurt by going back to juniors, but like I said originally, with Roy you can't really fault the team for sending him back but in an ideal world the AHL would've been a better place for him.