While I have not played role ranked as I am on EUW, I am not opposed to the idea of it. For players that are unable to commit enough time to league to learn each role to a similar standard, it is a good solution.
Saying that, there is the obvious issue of people not taking their game seriously if they get autofilled to a position other than their preferred one. While an opt in, opt out would help those not bothered about playing role ranked, it would not necessarily help those who do like the idea of role ranked. It does nothing to stop trolling.
In my opinion the solution is to have two different solo queue ranked modes, ranked normal and ranked role ranked. However on role ranked, you only pick one role and you are guaranteed this role, auto fill is not a thing. There may be a increased queue time for this, but in my opinion this is worth having a significantly lower chance of trolls.
I agree that people who can get to a high rank in normal ranked should be seen as superior players than people who can only do it on one rank and I think this should show. Different end of season borders or something of this sort may be the best way to solve this problem.