My general opinion still stands though - I don't think the writers need to dot every "i" and cross every "t" when it comes to background information, the audience are clever enough to fill these gaps.
I'm not saying we should know everything about a character, just that there has to be "something" to the character that fits with the their motivation that drives the story. Roga desperately wants to rejoin society. Ok, I get that. Now my next question is why? What's so special about rejoining a culture that willingly altered you for war and readily abandoned you when it was over? Did you have a job you enjoyed doing? Do you have a family? Did you have plans for yourself that you thought you could still pursue after you fought in the war? All we ever get is "We want our lives back. We want to come home." Yeah, well so do a lot of criminals who are still doing time in prison, and I bet there are a lot out there who have better reasons to rejoin society than Roga does.