I ranked close to 1200 after my placements but have had lost 3 games in a row today. My ad carries consists of Ashe, Cait, Corki, and Vayne and I've yet to reach a problem where someone else wanted that role. (and yes I can play different roles, just I prefer carry)
I tend to be passive early game, although I've tried a few times to deny and poke my opponent ad carries. I do make mistakes, I'm not perfect, but I feel as though when laning phase ends, if I'm above in CS and I have maybe an IE + zeal + cloak, and if other lanes have already struggled and may have fell a little behind. Half the times a good team fight breaks out and my team comes out ahead, but if the transition between laning to grouping gets sloppy, the game slowly bleeds out.
For ad carries, I feel like my game depends heavily on how well the other lanes hold within the first half of the game. I don't think I can afford to roam unless I have an early tower which is rare, what can I do besides playing another role?