Mike Laidlaw, Lead Designer of Dragon Age II shows in this video, the two different ways you can play the game:

-As an action RPG where you can play in real time.
The player can move quickly and get into position anywhere on the battlefield.  You can easily switch between characters use their different abilities to help finish the battle.

-Use the pause and play approach where you can issue the orders tactically.
With the game pause, the player can give orders to each character and strategist on how each of them can contribute to the battle. Then play the game to see the results. You can pause again to give another set of commands for each character.

Of course, you can also use these both. While playing in real time, you can use your favorite character while on pause you can give orders to the other characters. You can use any combination’s to your liking.