I don't have any particular "role" I tend to take up, since most RPs I end up joining aren't built with archetypes or an overarching plot already in mind. I usually prefer to just pick a setting and let/have people make characters as they will so their motivations are what drive the plot. Plus, my characters are all differentiated people-- on the one hand you have, say, the Pokemon Trainer version of my author avatar, Wry, who is pretty much me most of the time. On the other hand, one of my most beloved characters is a serial killer who uses necromancy to tear the animating force out of sentient undead, both to keep himself alive and because he's addicted to it (even though it hurts to "overamp" himself that way). He's pathetic and amoral, the twisted result of the "normal" version of that character having things turn out differently for him in the long run, and completely bent out of shape by the end of his story. Something demonstrative of him might be this:
Code:
[The muted clatter of boots on cobble, the tack-tap of hard leather and iron, bounces between narrow alley walls in a pattern like spider legs. Ahead, a more panicked staccato falls in and out of rhythm with it, occasionally stumbling into silence for a few moments while the unrelenting bass of bigger feet slowly catches up, unhurried.]
[Discordant scraping joins the beat after a minute as a plated gauntlet is pressed to and dragged down the brick wall of a nearby building, and a hoarse chuckle punctuates the noise as the steps ahead of him become all but hysterical. He passes a pair of ruined high heels that should have been abandoned long before this point, briefly illuminated by unearthly light and left to molder where they lie.]
[The feet ahead falter, fall, and scramble to the right, a thin moan of mortal despair floating back to him as he follows casually. She's pressed into the corner furthest from him, caught in a blind end and reeling as she faces him; her chest is rising and falling rapidly in an instinctual imitation of life, each breath out another choked-high noise announcing her to be moments from fainting.]
And here you are, [he almost coos, the sickly green light of irises gone bright and lurid lighting up her pale body as he steps closer.] Did running help?
[She barely pulls away, dizzy with fear, as he strips off his right gauntlet, slides the crook of his hand up her windpipe and presses against the hinge of her neck to hold her there. He leans close a moment as his hand becomes a vicegrip against her lifeless flesh, cinching off the meaningless intake of unnecessary oxygen as well as a final high noise.]
But then you have
this. And a whole lot of people in between "amoral wretch" and "ADHD-riddled optimist."