??? That IS role. When you role play, you're playing some personality. Maybe a nice person, maybe a mean person, maybe an eccentric, maybe somebody dull (though hopefully not), maybe somebody that can't deal with anyone else having authority, or maybe somebody that avoids personal responsibility like the plague.
No, that's a personality…
And if you play the exact same strict personality for more that a certain period of time then it becomes either a stereotype or a caricature.
Let's just take your first example: Nice person. Lol. For real? Apparently Hitler was a nice person. You can find a gazillion quotes of people saying he was very nice. He was nice to some and not nice to others.
What constitutes nice for you might not constitute what is considered nice for someone else, your entire 'roleplay' will just be you playing what you think is nice. You're not playing 'some role', you're playing yourself when you imagine yourself being nice.
And it's an entirely false proposition, because all beings are natural dichotomies, existing in perpetual duality. No being will ever be permanently nice nor permanently mean. Your imagination of role is merely a natural being stripped of all facets of themselves bar one specific trait, a trait that is exclusive to you and you alone. You'd be taking the nomenclature of toon to it's literal meaning of making, essentially, a cartoon character with all the depth of a repeated five minute cartoon, forever locked in as Dick Dastardly, always looking for the 'option' to lay traps for pigeons or racing cars with no singular objective or driving force beyond that one specific trait.
When you go to your job, whatever it may be, you have some kind of title. This identifies your role. What personality you have from day-to-day is irrelevant to the function of performing your role. If you quit your role and a new person took it over, they would have a singularly different personality to you but would perform the exact same role.
Your personality is what you personally bring to your role in surplus to the requirements of the position (or detriment). To take an example of an MMO team, the simplest means to express the point, the MMO usually demands the core of the team consists of three 'roles', the tank, the glass canon and the healer. If your healer is good or evil makes no difference to the role beyond character sheet specialisation, the actions they perform are the same. The only time the personality is relevant is occasionally deciding the direction of a quest or quest outcome, something that rarely effects either game or character progression, but just adds 'flavour text' to the adventure.
P&P parties are no different, people are encouraged to take on different roles. What choices people make with regard either quest direction or quest outcome are irrelevant to the role each player assumes and irrelevant to the progression of the characters. Individual personalities will effect only the flavour of the adventure.
Ergo: If you say that personality is role and that only personality is role then you are not speaking from the point of view of a role playing game, you are speaking from the point of view of a choose your own adventure where role is entirely irrelevant. And, further than that, you are creating a choose your own adventure where you aren't even choosing your own adventure, you're forcing yourself into a linear story experience where you're actively refusing to make any choices at all, you're just going through the motions of laying traps for pigeons as your answer to every crossroads, because you can only conceptualise something as not being you (ie: a different personality) by selecting one of your preconceived assumptions of character and turning it into a cartoon character - I'm evil, therefore I must lay traps for pigeons. Which is the most lazy way to play a game possible.
The reality of greater options via roleplaying is that by having a healer with you, whatever their personality, this then allows the DM the option to offer you the option to revive and heal people who would otherwise die, or whatever other character sheet trait the role brings - you decided to heal the dying Mayor, you gain 500XP and a new NPC to interact with instead of just the option to loot his/her corpse.
Whether you perceive healing the Mayor as good or evil or nice or mean will depend on other factors, factors regarding the flavour of the story, but that wont be roleplaying, that will be you making philosophical decisions that you justify however you want, as a person disassociated from your character sheet. The extent to which the gameworld agrees with your philosophical choice as being in line with your character will depend on the individual personality of the DM or developer, again, completely disassociated from any character sheet roles.
I can put this into an actual example:
You are playing as a rogue with a party of other RPers, you are the only one with rogue skills, the party finds itself in a room in a property that is not theirs, with no NPCs in sight:
DM: There is a box in the corner. It looks like a treasure box.
Party member 1, Fighter: Hey, Zloth, I don't like the idea of bashing that box, I think I'd make too much noise.
Party member 2, Healer: Now THAT'S a treasure chest!
Party member 3, Druid: I cannot seem to manipulate it, it seems to be mostly metal in construction.
They all look at you.
They look at you because this situation is a situation for your "role" in the party.
It doesn't really matter what your personality is here. Either you're going to go have a go at the box or you're not. Of all the myriad 'personalities' you could apply to this situation, your 'choices' are still pretty much binary, you either perform your role or you don't.
If you choose not to and you use your personality as an excuse then you are not roleplaying not examining the box, you're simply refusing to perform your role, for whatever reason. You're "wasting everyone's time". Why did you pick a rogue if you are going to then contradict that choice by 'choosing' a personality that has a likelyhood to not want to perform it's role.
If anything, personality is more anti-role than role, and yet you seem to be under the impression that it's everything about role. And I have no idea why.
The increased game options occurred precisely because your role added an extra option to the party. Your personality did not add any options and, in fact, your personality only has the possiblity to reduce options in such a scenario, reduce them back to where it would be no different than if you weren't even in the party in the first place.