I've always assumed that RPGs were characterized by their gameplay tropes rather than their definition, cuz' "assuming multiple roles with each having differentiated purposes" doesn't sound interesting enough to justify a genre, well, nothing sounds interesting enough to justify genre by itself, but whatever. So, in your opinion what genre does KH and DS fall in? I'm curious. I'll still call them ARPGs cuz' definitions are subjective n' shit.

^ This

Where is the cute girl with the big eyes and blonde/pink hair...

Exactly. Although, you missed the obligatory bimbo with a chest with each boob being as big as her head, the spiky hair dude, the shy flat-chested girl, and the fact that every single human being looks like an overgrown baby.

@Bold I was just like that until the few and I put some effort to find the actual definition ... 

I know the definition may not sound interesting but in hindsight when you start thinking about it there's a lot of intuition behind that statement ...

The very first RPG, D&D was defined by it's "character class" such as mage, warrior, etc. There were other mechanics such as race or moral alignment but anyone would reckon that those things don't define an RPG otherwise there would be no difference between D&D or Bioshock, Far Cry 2, you name it with another FPS that has a moral system or specific playable races. 

This made tons of sense seeing as how each of those roles had specific purposes in battle or elsewhere. A mage specializing in magic and the warrior specializing in melee combat were the very sound things about RPGs having "multiple roles with each having specific purposes". A mage been able to do specific to everything a warrior can or a warrior been able to cast every spell a mage could had meant that having multiple roles makes no difference therefore you end up having one role in the end which means that the "character class" in that said game is a side mechanic, not the main mechanic which defines an RPG. 

A character class without limits or restrictions and not been able to assume different roles only means that the said game CAN'T role-play ...

So in my backed up opinion, games like Kingdom Hearts or Demon's souls fall under action games or as I would like to say pseudo RPGs ...