Before you start you should specify that in this kind of games there are heroes who are born to fill some roles and heroes are born second role for others. As in all MOBA also in HOTS it is essential to be part of a GROUP according to the role that has been assigned:
WARRIOR - The hero fighter par excellence, perfect in battle but must always act, taking with him a group of allies and be able to fall back when needed. He has a large number of HP.
SUPPORT - Hero must support group and more likely to curative actions rather than to actual combat but their management may depend on the outcome of a game.
SPECIALIST - Heroes very specific ranging to satisfy that segment of players who did not find evidence in other classes. These characters have powers and abilities that should be placed in specific types of groups.
MURDERESS - Perfect for killing, if you need to quickly eliminate an enemy you just need to call a murderess silent and lethal. These heroes are also able to move quickly and disappear quickly after clearing the target. It has a high attack power.
The following video shows more details for any role: