[[WMG: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 [[VideoGame/FinalFantasyVII Cloud]], anyway.
** [[spoiler:{{Jossed}}. Although he is considered the son of the demon king, it is made clear that he and Rchimedes are fully human.]]

[[WMG: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 ([[spoiler: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 JerkWithAHeartOfGold anyway. Maybe he's only secretly related or something. [[spoiler: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.
** [[spoiler:{{Jossed}}. He's the hero Creasion...though Ros AND Creasion are fake names.]]

[[WMG:Alba will TakeALevelInBadass.]]
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.
** [[spoiler: Confirmed. In the manga, at least.]]