One of the important roles is to know how to peel someone off a carry, by either getting in their face, or having enough CC to make them never make it to the carry. If you have enough peelers (or your character is not good at it) then its usually your job to get after their carry and chase them out of fights. Assassins are a lot harder, as they're usually very squishy, so getting caught before taking their target out usually means their dead.

As a melee/close range champ, you usually need a decent amount of durability to be able to *make* it to the combat, as an easily killed champion running into the enemy lines usually doesn't last very long.