Separate Queues for each role would create less rage, trolling and intentional feeding
The following are not problems with role queues because:
The Meta - Riot doesn't want to change the meta, there will probably still be 5 roles in a new meta. Break the meta with your team, not in solo queue
Trolls - Need a way to report people not playing the role they said, pretty easy
Role Popularity - Wait a bit longer to be guaranteed your favorite popular role, or play one that is less popular. Not a bad tradeoff imo
Elo - It is a matter of preference to decide how it should work
Riot will decide how they want to implement it, but I would prefer to be able to see how good someone is at each role in regular solo queue
You might be able to sway them, or me, so discuss.
As for the technical difficulty of allowing people to queue for certain roles, I am a computer science student and know how to implement Elo and TrueSkill. This suggestion is not trivial,and it is work but it's not super hard. or impossible.
Riot could allow players to queue in multiple roles and still exclude some roles; either using checkboxes or a click and drag system.
I'm not suggesting solo queue disappear, but people who want to follow the meta can find teams. It's sort of an LFG for mobas.
Wall of Text
There is a lot of discussion in the community about trolls and feeders, and how if people don't get their preferred role they will do what they can to throw the game and be as annoying as possible. "Mid, or I feed" etc.
I know that there is the Tribunal system which eventually punishes people who do this enough, but isn't prevention better? Doesn't it make for a better experience? In addition, it appears that at higher elos people report less often and griefers, and trollers still abound.
If you could queue marking which roles you prefer to play and which you do not want to play, and matchmaking respected that, average game enjoyment would go up. Quite a bit, I think.
Yes, there are some possible issues: Riot may not want to cement the meta or the meta may change, some roles might be too popular, people may still troll and refuse to play the roles they said they would, and there are question about how this interacts with elo scores.
Let's discuss each of these:
It seems to me with the ongoing Jungle and item changes for Season 3, that Riot accepts and accommodates the meta. It doesn't appear that they want to shake up the meta too much, but tweak for a more fun experience. Great! What about people who want to break/change the meta? That is cool, and can be super effective for your ranked team or by teams like M5 in a tournament. My contention is that no one wants to be on a team with the guy who wants to break the meta by himself. The place to do that is not solo/duo queue but with your buddies or a whole team.
Now if the meta does eventually change away from the current five roles, which seems doubtful without some drastic changes from Riot which do not seems forthcoming, what then? We may have to shut down role specific queuing, but probably not. There will still be 5 roles on each team, perhaps the actual roles or duties of each would change, but you could queue as the old name until Riot catches up.
It is however possible that the meta could change in such a way that that does not work. Perhaps a bit like bot lane's burst, poke, sustain interplay. On the off chance of a metaclysm, role queuing would not help the cries of "Poke comp or I feed", but perhaps comp queues would... Anyway, people would probably stop using role queuing and Riot might end up shutting it down. But until then games should be more enjoyable with less rage, feeding and trolling because people can get the roles they want as long as they are willing to wait a bit longer in the queue for the most desirable ones.
Role Popularity and Abuse of the Role Queues
Riot hopes to make all roles equally desired to be played, which is an admirable goal, but until that is achieved, how would role desire imbalance affect role queues? It's pretty simple. Some queues would take longer to pop. In a hurry to get in game? Maybe you don't mind playing support or jungling all that much after all.
Maybe some people still do and will queue in the less desirable ones but pick an ad carry. Or maybe this will just provide another way for people to troll. What then?
In champion select (and the score screen hopefully) the UI should state what role they queued for and have an option to report for not playing/picking according to assigned role. The Tribunal could look at those very quickly. It's pretty obvious if someone is not playing a certain role, they're in the wrong place and by just watching just one game, judgement could be passed and warnings or maybe temporary suspensions from role queues assigned. One might want to let the team vote to dodge after picks based on if a player picked a champion that cannot play the role they picked, but it would get abused pretty heavily.
Now people could abuse this new report option. The idea is for players to report for not playing a role, but the Tribunal should be encouraged to only warn if it is bad. I.E. They are actually playing top lane or ad carry when they queued as support. This doesn't mean that people should report Lux or Zyra support with the new report option. You don't have to queue in a role if you really want to play bruiser and adc bottom lane. Solo queue can carry on its merry (or rather angry) way.
Issues of Elo
Most of the problems with elo seem to be problems of preference, not good or bad. You could have the role queue games affect your solo/duo queue elo. But I would prefer separate elos for each role, and for them to be visible. They could be hidden, whatever. How about at the beginning then? Perhaps use their solo elo to seed all the roles for the placement matches. Maybe allow them to say they are bad at the role to play their placement matches from the starting elo (if less than their current elo of course).
Perhaps you have an objection I haven't addressed or you like the idea. Let's discuss it.