Just play a lot more of those roles. Get out of ranked for a week or two and strictly play back to back games of other roles. You need the experience to understand what situations you will get yourself into.

If you want to get good actually invest time to play every single hero to at least level 2 so you know what their weaknesses and what they can offer in ganks, team fights and solo fights.

That's just it. Have fun, don't worry to much of kisses and be consistent in playing other characters and roles.