I have added three difficulty ratings to each role. For every role, each of these is important, but some are more important than others to be particularly good at.
Piloting: The mastery of controlling your mech. This means things as being able to dodge slow-down from cliffs, torso twisting and fast movement control. Roles with a high rating will require more skill in maneuvering than those with a low rating.
Aim: The mastery of hitting your targets. This means things like...
Roles: More than a weight class!
A guide on mech roles and their most important aspects in a build.