Ros is a demon.Other than his being a Badass, this could explain his super strength, which seems on par with the known demons so far. ...Or he could just be a Badass. He's pretty much a dark palette swap of Cloud, anyway.
Ros is secretly one of the 12 Chosen Ones.Going along with the demon theory, I can't have been the only one to notice his tell-tale red eyes; both Dezember and Janua have black hair and red eyes as well (although in Janua's case it's heterochromia, with one blue). Alternatively, he could just be related to one of the two—which would have be an added reason to save Janua, other than his being a Jerk with a Heart of Gold anyway. Maybe he's only secretly related or something. Elf November showcases that you don't need to have the month in your first name, either (if Ross isn't just a fake name he goes by). Rchi-chan not knowing or noticing could be explained by her young age (maybe he left a few hundred years ago; she's only 100) and his being more powerful than her. They also rarely if ever bring up his name in-series, and it could be that, if Rchi-chan knew it, she'd suddenly realize he was a demon who'd left a long time ago.
Alba will Take a Level in Badass.Come on; he's the Hero, after all! I certainly hope so, but it is a comedy series after all, so perhaps not. Though, even if he does, he probubly still wont get any respect.