Yeah i agree. This is the reason im not playing ranked with my friends because they want to play dedicated roles even though most of us can play various roles. I think its not only needed to be able to play each role but you need to play each role well.
Still i usually main mid or top.
I'd prefer playing this role over that role. It's not that I'm uncomfortable with the other role or anything, it's just that I enjoy playing this role better.
Which is a problem because I'm bored of playing ADC sometimes. Even though among my friends, they probably think I'm the most fit for playing ADC >_> Eh. Do whatever it takes to win for the team, I guess. It just gets boring after a while.