At first I thought the role's are a fun addition. While they don't really add anything useful it's fun to check whether the guy you see as your key player is actually also the key player according to these "objective" (they are objective actually, not perfect...but objective) measures.
But last time when I was checking the transfermarket I almost dismissed a player because he had "back up potential" (while it was actually an MVP). Now this might be just me being a bit stupid, but I do think that it might be harder for beginners. When looking for a trainee they have to learn that age, potential and length are important...but not player role. Especially since the potential and player role lookalike and have pretty similar terms I can see that it might be confusing.
Combined with the fact that it doesn't really add anything gamewise (it influences nothing) I'd say we save the space in the player profile for more useful things.
Crunchy! If you eat fast enough