| There is an interesting history behind why we use this word the way we do today. PikeWake and goneaway give explanations for the ways we use the word. However Webster1913 is more closely related to the origin. In William Shakespeare's day (and perhaps before, but I don't know as much about Before Will) "role" was the spelling for what is now called a "roll" (noun) as in thing that is rolled up. Sushi, sleeping bag, blunt what have you.
With that in mind, let me tell you that it went like this:
Bard-boy would sit down with his nice quill pen and scribble out say, Pericles. It was rumored that Will "never scratched out a line." This is not just a modern day idiom expressing his genius, but something that was actually said of him while he was alive by his contemporaries (rivals) as a way of insulting him; calling him a sloppy playwright who simply produced the first-thing that came to mind. At any rate, you can imagine that what he scribbled out at odd hours of the night with a quill pen and probably onto less than high quality paper, was not the most legible bit of drama ever seen.
Now we all know that by 1600, the printing press had been in use for over a century. But these are actors we're talking about. The "Starving Actor" concept is not a new cliche. Printing something on the press was expensive! All Willie needed was a way to make it faintly more readable before giving to his actors. So he took this collection of ink-soaked napkins to some literate friend of his, a "scribe" by trade. For the price of the paper and maybe a tip, he got a new copy of the script, neatly written out. But you can imagine how long it would take to transcribe 15 copies of Macbeth much less Hamlet. So the scribe would make ONE new copy, and give it back to Shakespeare, probably within 24 hours.
Now came the fun part. Shakespeare proceeded to cut up this one version of the script. Oftentimes the scribe kept the original version, presumably to be discarded later. (More on the bootlegging of Shakespeare later) Shakespeare took the new version, and cut it up according to actor. The cut ups were pasted onto leather or cloth or something, and ROLLED up like a scroll. All the actor received was a copy of his or her own lines. Presumably the disciplined actor would try to write in as many of his cues as possible. However, usually no one had more than two days to learn all of their own lines, much less their cues. (See: Shakespeare is like Sex: A beginner's guide for alternatives to learning your cues.) What they got was what they themselves had to get out there onstage and say. Tied up in a roll. Or in that day, a role. Which is why nowadays, when you get your "part" in a play, or any other walk of life, you will be playing what is contained within your particular "role."
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