Blizzard has posted the design intended roles for each class on their forums. Their intended role for the Druid class shouldn't surprise too many of you:

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The Druid has three potential roles in a group. When in their normal, biped form, they act well as a healer and can give support in the form of buffs and debuffs; they also have limited crowd control against dragons. Their Bear form gives them offensive and defensive power enough to step up to a monster and take the hits (we’re looking into aggro management for the form). In Cat form, the Druid becomes a damage dealer. This trio of roles in one class gives the Druid a diverse feel and allows them to perform nearly any role perceived as “needed” in a party.
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<hr>- Caydiem -
Assistant Community Manager, WoW

You can read about the other intended class roles here (http://www.worldofwarcraft.com/thread.aspx?fn=wow-general&t=470726&p=1&#post470726) or on the forum for each class (http://www.worldofwarcraft.com/forums/#classes).

Have some thoughts about the Druid's role? Discuss them here (http://wow.forums.thedruidsgrove.org/showthread.php?p=114456#post114456).