A rogue’s evasion ability and a troll’s ability to regenerate are extraordinary abilities. These abilities cannot be disrupted in combat, as spells can, and they generally do not provoke attacks of opportunity. Effects or areas that negate or disrupt magic have no effect on extraordinary abilities. They are not subject to dispelling, and they function normally in an antimagic field. Indeed, extraordinary abilities do not qualify as magical, though they may break the laws of physics.
Using an extraordinary ability (such as a barbarian’s uncanny dodge ability) is usually not an action because most extraordinary abilities automatically happen in a reactive fashion. Those extraordinary abilities that are actions are usually standard actions that cannot be disrupted, do not require concentration, and do not provoke attacks of opportunity.
Source: Player's Handbook
