Role playing is great, but it needs to be based around something... like the combat that will occur on a mission, or a rivalry between the kingdoms of the players. Role playing often happens during combat, the two are not mutually exclusive.
As a DM I like to allow my players to gain a stake in the world, and they know that their actions and decisions will have far reaching effects.
Pure role playing (in town, or without a threat) can only take you so far, there has to be a dynamic coming from the players based on what they have survived, and what they want to accomplish. And good role playing often happens when the players' characters are under external threat.