Yeah... being forced to do anything when it comes to pnp rpg's tends to be really annoying... and can lead to conflikt amongst the players, and between the players and GM. It is one thing to be "stuck" with a certain role due to that you as a group talked amongst your self about maybe how the groups characters should be structured to cover as many different bases as possible... then atleast there has been a conversation about it, where you your self has been able to say "yeah, sure, I can play the groups main healer/medic" even if you don't normally like playing such a role maybe (I my self don't really like those roles... I tend to more lean towards the warrior/soldier types of combat roles). But when your told, forced, to play a role... either by the other players, or the GM... then things can tend to turn bad, especially if it keeps happening over and over again. There is also a difference if it is something like where the GM maybe force everybody to play Mages or what ever, since then it comes down to that the story/campaign the GM wants to lead revolves around everybody being a mage of some kind.
Luckily I have only ever once been forced to play a certain role once, when the others in the group was not forced at all and could make what ever they wanted. My GM had finally goten tired of me for the past 10 or so years almost only ever playing human warriors/soldiers, or something close to it (like a combat heavy type of thief/rogue/rangers/hunters/etc kinds of characters, etc)... so while the other 2 in the group got to play what they wanted (both of them made Dwarves), my GM forced me to play an elven mage. Which are two of the few things I dislike the most playing... playing mages and such is the roles I dislike the most playing... and there are not a lot of races I in general dislike even more playing then Elves (Dwarves usually being the race I dislike the most playing). I still got to choice exactly how to build the character, as long as he was an elf mage, and atleast decent at magic and no weapon or combat skill higher then any mage skills (which was another stipulation ... since that is also pretty common for me when I made characters who's role was not really combat, where even something like a scientist would be better at combat then he was on the science stuff when I made them... I either make pure warriors/soldiers... or hybrid roles/classes where one half of them are warriors/soldiers types of characters... XD ). The character I decided to make was essentualy a sort of protest towards that I was forced to playing that character. Everything from which magic school I choice, to his name, personality, etc.
Of course, it is not really that I mind playing something like that... a mage, or something which is not a human (I tend to prefer playing human in essentually all types of games, be they pnp rpg, tabletop games, or videogames in general), etc... but I atleast want it to be my choice when I do play something like that.