So out of 15 games(10 streak + 5 promos), you had 13 as your main, and 2 as your secondary? That is 86.6% of the time you got your main role. _You poor thing. _
I main support, which means that my cs'ing skills and "do-not-attack-the-other-laner-constantly-because-you-need-to-farm" skills are terrible due to lack of practice, and I still manage to avoid feeding or becoming behind in all roles except jungle(there I feed my teammates, I cannot get a single kill for myself...) a large % of the time(with how little I have to do other roles that isn't really hard...). That may put the burden on my allies to carry the game, but I at least do not drag it down.
Its better than when your chance of getting your favored role was 20%, which was increased or decreased by your teammates workability and preferences.