You'll need access to the Black Emporium and enough gold to afford the Maker's Sigh potion (which resets all Ability Points/Attributes). Hawke's uniqe preset skills mean that when you use a Maker's Sigh potion and save, the preset skills will be always be filled. You can exploit this by following these steps:

1. Use a Maker's Sigh.

2. Save your game and reload the file.

3. Examine your Ability Points -- you should see the amount removes plus Hawke's preset abilities. For a Rogue this will be 4-5 points in the fual-wield tree.

4. Use another Maker's Sigh to add those Abilities to the Ability Points. You can repeat this indefintiely provided you have the potions, just remember to save and reload each time.