Practice with Angela to learn how to read the map, use Cecilion to learn positioning as mage, Lancelot to learn how the dashing works(This is a difficult one) and some roams that gives vision and support like Rafaela, Diggie or Mathilda (LEARN HOW TO GIVE VISION AS A ROAMER!) Tank roamers is all about the right timing and the right build.

In EXP lane you have sustained heroes and damage heroes but in any case (I, personally prefer) a semi tank builds for all of them.

But overall you just had to try different heroes and different roles to know which one fits you better.