So this has been quite a problem in many of my games so far, and we all know it's only going to get worse when it goes live, so we should probably have a solution in place beforehand.
How should refusing to play your second role and instead locking in your first role be dealt with / possibly punished? Just make it reportable and a light punishment of some kind? (It really shouldn't be a harsh punishment, but it should definitely be enough to deter it).
I've had plenty pick adc/support, get support, and since they were first pick decide they want adc and lock one in anyways. I've had people say they're playing top anyways because it's what they want even though they were assigned jungle, and I'm sure others have had this too. I know we shouldn't absolutely force the meta on everyone, and I know some people actually like their fun MF supports or kindred top. We should definitely work on a solution to prevent the toxic behavior of playing what you want anyways though, since the whole point of this new champ select is to remove this type of toxic behavior from the community.