I honestly think this is the way autofill should work though.
Yes, you're willing to wait longer to play your role. However maybe your 4 allies have already waited 15 minutes for their role (exaggerating here but let's see the point out). Now, what's more fair? You queue and get put in to your preferred role instantly, while someone who's waited 15min gets filled? Or you queue and get filled instantly (but don't have to wait in a queue) and the guys who waited 15min get their preferred roles (that they waited for).
The way I look at it - it was just your turn. A fill was needed and you were due to be filled, and so once you queued up it figured "why make this guy wait he's getting filled anyways. We have 173 games that just need a support right now, we're getting all other roles queued for at a rate of 20 per minute, and we're only seeing new supports at a rate of 10 per 45 seconds. It's only getting worse, let's get 4 people in to a game and let this guy spend 25 min playing as support instead of 15 min waiting in queue. Then he'll get what he wants next game and someone else will get filled with a short queue."
You know what sucks? Waiting in queue for 10min then getting autofilled. Or waiting in queue for 5min, in champ select with preferred role for 4min, getting dodged, in queue for 2 min, in champ select with preferred role again for 4min, dodged again, in queue for 2 min, in champ select with preferred role again for 4min, dodged again, in queue for 20 sec, filled. Yea - that sucks. Getting filled quickly when you queue up? Not so bad in comparison. Honestly, I wish that was how it works more often (also wish everyone would just take their turn when filled instead of dodging). Although autofill warning doesn't help - with the warning always up it's meaningless. If they'd actually let there not be autofill at certain times then maybe the guys who really don't want to fill and dodge out of it would just queue at the times it wasn't active...