Dealing with trolls before the match has even begun

So we all know we can pick 2 roles before we start. When i actually get into champion select, some guy wants go jungle/top/mid while i picked that roll. He bans my preselected champion, then picks my role. How do you guys deal with this? I've dodged queue a couple of times now, but its got up to a point where i have to wait 30 mins before the queue ban is over and it gets annoying.
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