Does the Sneak attack bonus ( +2) only apply to damage roll, or it applies to Attack roll as well?
"The rogue's attack deals extra damage anytime her target would be denied a Dexterity bonus to AC (whether the target actually has a Dexterity bonus or not), or when the rogue flanks her target. "
What do they mean by "Denied a Dexterity bonus to AC"? can you give me an example?
Can you use sneak attack twice in a turn if you attack with both daggers?
See CONDITIONS THAT ALLOW SNEAK ATTACKS
And yes it is per attack as long as the conditions you quote are met.
when you feint, when you haven't performed an action yet in combat, if you have total concealment from someone, when they're tied up on the ground, or effected by hold person.
the +2 you;re talking about I think you mean flanking, which is only to hit.
Sneak attack does a number of d6s of damage.
Does the Sneak attack bonus ( +2) only apply to damage roll, or it applies to Attack roll as well?
I'm not sure what you are talking about here. There is no +2 Sneak Attack bonus. Sneak Attack only adds a certain number of extra damage dice.
"The rogue's attack deals extra damage anytime her target would be denied a Dexterity bonus to AC (whether the target actually has a Dexterity bonus or not), or when the rogue flanks her target. "
What do they mean by "Denied a Dexterity bonus to AC"? can you give me an example?
It means you don't get to add your Dexterity modifier to your AC. Several conditions apply this, such as being attacked by an invisible attacker.
Can you use sneak attack twice in a turn if you attack with both daggers?
You can apply Sneak Attack damage to any attack that qualifies. If you have 10 attacks a round, and they all qualify as sneak attacks, all 10 get sneak attack damage.
"Denied a dexterity bonus to AC" is a psuedo-condition in the game. There are certain times when an enemy specifically can't "add their dexterity bonus to AC". These times include being flat-footed (which makes it so you don't add your Dex bonus and makes it so you can't make attacks of opportunity), being a defender against an invisible foe or a foe you aren't aware of, etc.
Yes, you get sneak attack on every attack as long as the subsequent attacks qualify.
Example:
You're invisible, and you have two daggers. You sneak up on a goblin guard (who, despite the on-going combat around you, is more preoccupied with picking his nose than being a useful guard), and attack him with your daggers.
You attack with the first dagger, and hit. You now add your sneak attack to the damage to the dagger's damage. But, you are no longer invisible. The enemy can see you, and can react. This means that your second attack is NOT against a foe that is denied their Dex bonus to AC, as you are no longer invisible. So unless they haven't acted yet (they have, you're in combat with a bunch of other goblins), or you are flanking the foe (a psuedo-condition unrelated to being denied Dex bonus to AC, but one that also allows you to sneak attack), your second dagger won't get the sneak attack damage.
But lets rewind say that you were flanking the goblin with another ally. Your first attack roll will be against the AC of the goblin minus his Dexterity bonus to AC, +2 (from you being invisible), and +2 from flanking (yes, you can flank while invisible. It's weird). You'll qualify for sneak attack. Your second attack will be made while you're visible, so it'll be at the normal attack bonus, but since you're flanking, you'll get the +2 to hit, and will also deal sneak attack damage.
If you need a multitude of Dev Commentary on this, let me know, but I think my post covers it already :)
Your first attack roll will be against the AC of the goblin minus his Dexterity bonus to AC, +2 (from you being invisible), and +2 from flanking (yes, you can flank while invisible. It's weird).
So the +2 from flanking only applies to the attack roll and not the damage roll?
Thank you for all that info, it was very clarifying :)
So the +2 from flanking only applies to the attack roll and not the damage roll?
Correct.