Ranked Roles Question

[Dot.A]

Just had my 4th ranked game.
Role Queue, Not Calibrated, all 5 roles checked, Ranked All Pick.
Entered in a party of 3 including me.
My teammates and I agreed they will go offlane and support, and I will go mid if possible.
In lobby after ban I marked mid lane and picked.
Immediately the other 2 players started shouting to ban me, which they kept all game.
After the game my teammates explained that the game assigned me to hard support, even though I checked all boxes going in, which disrupted the other 2 players' intentions.
Looked up the Matchmaking entry and I am still short of explanations.
- Why did the game decide role for me ?
- How can I tell in lobby which role the game chose for me ?
- Should I check only one box ? None ?
- Is there a thourough guide for players transitioning from Normal to Ranked ? The official page I read seems to assume a lot of knowledge on the reader's part.
Cheers : )

[Zagryzaec]

1) you only get ONE role in ranked. Not several to choose. The role you got is written under your name on top of the screen in pick phase.
2) you can check as many roles before search as you want but FROM THESE CHOSEN ROLES YOU ONLY GET ONE.
3) you will never get the role you didn't check.
4) role you get isn't just random, you will get most needed by community role from chosen. Now it's mostly either pos5,3 or 4. You will never get pos2 or 1 if you checked other ones, as too much people want to play those.
5) you can get the role you want by spending tokens and checking those roles. You get tokens by playing roles that community needs. Those are marked with stars.
6) if you don't understand anything ask your teammates in game.

[Highrule -1]

His party should've explained RQ to him before they started...

[Dot.A]

To Zagryzaec : Thanks for detailed response !
I understood except for 5) :
- I can get the role I want ( e.g. pos1 ) by checking only that role in search ?
- for every game I check all 5 roles in search before game, I get 4 games where I am allowed to check just one, ensuring I get the role I want ? Is this what you meant be spending tokens ?
- I played 4 ranked games so far and checked all boxes in all of them, so I should have now 16 games where I can check just one box, right ? But when I place the cursor on the "i" next to the green "Role Queue" I see a bar with a small green part streaming arrows, without a number. Guessing from the green part relative to the black part, if the maximum is 60, I have 4-5 1-role games left.
- what happens in Classic Ranked ?