Guarantee of roles during placement should be your main role.

I'm a Jungle/Support main and been playing league more often recently on account of my schedule freeing up. And here's my frustration with the current queuing system. So when queuing up for rank i select my before mentioned roles. I usually get stuck with support even though jungle is my main role. No biggy, its my secondary for a reason. My gripe is when i get into promos.

Its frustrating because I don't care to be guaranteed my secondary role, i get placed as support a big chunk of my games anyways. Guarantee me my main role. I don't care if queue times are longer. It's my main role for a reason and these games carry more weight than others.

It would be nice if Riot can improve on the current system it has by making auto-fill optional. There are players out there that don't care to wait extra long if it means they get their role. Those players are only proficient in one or two roles (or only have fun in those roles) so why should they be forced into any other role? That was the whole basis as to why you implemented dynamic queue in the first place. So people would not worry about the role that they get.