You don't have an "adc" assigned. The player is assigned "bot" role. He wants to go Nunu bot? He's allowed to. Nobody will ever be punished simply for their choice of champion and/or summoner spells. People will not be punished for trolling behaviors unless they actually troll. There is no enforced champion/role/build/summoner spell combination. Period.
You know what I'd do if I or a friend had first pick and a teammate decided to ban Senna after she came out? I'd go Veigar or Cassiopeia bot lane with heal and exhaust. You know how many of those games I lost? Less than 20%. You know what's even better? I know for a fact that those people got pissed off that they knew I did it only because they were a jerk and banned my champion.
Is that trolling? I mean, if Riot changes the rules, sure it may be. But under the current rules, I'm allowed to pick whatever champion I want for whatever reason I want. As far as the current community consensus goes, nobody actually wants "role locking" like they have in OverMeme.
Anyone know if they're going to keep it in OverMeme 2 given the amount of backlash they got for implementing it in OverMeme 1?