When using Raid Finder for the Dragon Soul raid instance, players whose currently assigned class role (Tank, Healer or Damage) matches the class role that a piece of armor or a weapon is flagged for will receive +100 to their Need roll. For purposes of this check, your currently assigned role is defined as the class role you have assigned when a boss is defeated. Sound confusing? I hope not, but here’s how it’ll work:

• A boss dies and drops EPIC TANKING ITEM.
• A mage in the group yawns and clicks the ‘Greed’ button, getting a 98.
• A Fury warrior in the group wants to take up tanking, so he rolls ‘Need’ and gets a solid 64.
• Both tanks want the item. Tank 1 rolls a 12, and Tank 2 rolls a 7.

So what happens?
Because the mage rolled greed, she’s right out from the start. The Fury warrior’s Need roll was higher than the tanks’, but he was in the Damage Dealer role when the boss died, and the item is flagged for tanking, so his 64 is still just a 64 out of a possible 100. In contrast, Tank 1 and Tank 2 each get a 100 point bonus to their rolls because they were in the Tanking role when the boss died and they’re rolling on an item that has been flagged for the tanking role. That means that Tank 1 rolled a 112 out of 200, and tank 2 rolled a 107 out of 200. Tank 1 wins the item! If a roll got a bonus, that bonus will be clearly displayed in the chat log.

Please keep in mind that, at least for now, this system will only look at class role, and not player spec. This bonus isn’t only for tanking items either — it applies to Tanking, Damage Dealing and Healing items, and some items are flagged for more than one class role too. Starting out, only Dragon Soul raid items will be flagged for class roles in this way (though all of the items in the raid will be flagged for one or more roles). As you might expect, all the normal Need Before Greed rules are still in place, so that means that these roll bonuses won’t overrule normal class and usability restrictions. Item tooltips in the raid won’t reflect which class roles will get rolling bonuses, but it should be fairly obvious based on stat allocations and item type.

We are considering expanding this system to apply to the new 4.3 dungeons as well, though it is unlikely that we’ll see the system apply to older dungeons or raids for now. Also, please keep in mind that this system is newly minted, and it may see further changes before it’s released with the Raid Finder in patch 4.3.

[Source]