Mob has an attack that if sucessful grants a grab attempt.
Goblin has the Roll With It ability feat.
Mob attacks the Goblin and beats the Goblins AC. The Goblin is to be dealt 18 damage followed by a grab attempt that would be easily sucessful. The Goblin rolls a 25 to "Roll with it" to avoid the damage.
Does grab apply before "Roll with it"?
Grab is not a rider affect that depends on damage. Even if the goblin had DR that negated the damage the grab should be initiated.
Roll With It assumes you can move. I would say that as soon as you are hit the grab attempt takes place so that goblin is not going anywhere.
As an example when an animal bites you it sinks in, it does not make a second grab attempt, even though the game requires a 2nd attack roll.
edit: In the end this will be a GM call but that is how I look it.
I could have sworn there was a rule that said if you take no damage from an attack(such as from DR), the grab does not apply. I can't seem to find that rule right now though - not sure if it was actually a houserule or not.
There is a rule similar to that.
Whenever damage reduction completely negates the damage from an attack, it also negates most special effects that accompany the attack, such as injury poison, a monk's stunning, and injury-based disease. Damage reduction does not negate touch attacks, energy damage dealt along with an attack, or energy drains. Nor does it affect poisons or diseases delivered by inhalation, ingestion, or contact.
The things it stops are things that require an injury to take place. Grab does not require an injury, only a successful attack.
Sammy, I believe that Mark is wrong in this case. His comment seems to be an off-the-cuff statement that is too broad and as a result contradicts the written rules. If we take Mark's statement at face value, NO rider effects would get through if DR reduced the damage to zero and that contradicts the quoted rule.
As per the quoted rule, not all added effects are negated by DR.
Regarding Grab specifically, there are monsters with non-touch Grab attacks that do ZERO damage (example, Bestiary 1's Octopus). Clearly, Grab is not damage dependent.
Grab (and Trip for that matter) are not doing anything to the internals of a body like Poison, Stunning, or injury-based Disease require.
If DR stops all damage, then riders like trip and grab would be negated.
Remember that Damage Reduction is an actual game term with given effects, and only when the damage is negated by Damage Reduction itself (and not a pseudosynonymous form of damage reduction like Incorporeality), does it negate rider effects. Also keep in mind that it works only on most special effects, not all of them. (Though Mark Seifter's post does imply that special effects that provide combat maneuvers would apply to a Grab ability.) With all that said, if the feat specified Damage Reduction (the game term), the Grab would not be applicable if the Goblin was able to negate the damage.
However, since the feat makes no such distinction, the Goblin's screwed (it's a Goblin, what else did you expect to happen?).
If DR stops all damage, then riders like trip and grab would be negated.
Mark is incorrect. Like I said, actually what the book said only damage dependent rider affects are stopped.
Let's take stunning fist as an example, which is also listed.
Benefit: You must declare that you are using this feat before you make your attack roll (thus, a failed attack roll ruins the attempt). Stunning Fist forces a foe damaged by your unarmed attack to make a Fortitude saving throw (DC 10 + 1/2 your character level + your Wis modifier), in addition to dealing damage normally.
Grab (Ex) If a creature with this special attack hits with the indicated attack (usually a claw or bite attack), it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity.
While grab assumes damage will take place, the only requirement is that the attack hits. It does not say if the attack hits and does damage. It is says that if the attack hits, and then goes to list the results of that hit.
Trip (Ex) A creature with the trip special attack can attempt to trip its opponent as a free action without provoking an attack of opportunity if it hits with the specified attack. If the attempt fails, the creature is not tripped in return.
Also trip only calls for a hit, not damage which falls in line with everything else I have used as an example.
True, the goblin could bounce before the grab attempt, and "what is negated" does need to be codified more.
Regarding Roll with It, it is an immediate action and like all immediate actions, it interrupts other things, such as the grab check.
Attack->Damage->Grab check
With Roll with it it is:
Attack->Damage->Roll with it->Grab Check(?)
If an immediate action negates the damage and moves your out of range of the grab check then there is no longer a grab check to be made.
The quote you provided states attack, damage, free action. At best it is attack, damage and free action (simultaneous).
Either way, the immediate action is resolved before applying the resolution of the attack. That is how immediate actions work.
Regarding Roll with It, it is an immediate action and like all immediate actions, it interrupts other things, such as the grab check.
Attack->Damage->Grab check
With Roll with it it is:
Attack->Damage->Roll with it->Grab Check(?)If an immediate action negates the damage and moves your out of range of the grab check then there is no longer a grab check to be made.
I never really thought about it this way. Then again, there aren't many Immediate Action abilities that allow stuff like this. In that case, it wouldn't matter if the reduced damage from the feat is Damage Reduction or not; as long as the check is successful, the move is executed.
Of course, since the Grab ability specifies an action to be taken (and instead of it simply being an additional effect to the attack, such as a Magus using Spellstrike with Shocking Grasp), it couldn't be taken.
One could assume that being moved from the square provokes AoOs, but there is an interesting tidbit from the feat:
This involuntary movementprovokes attacks of opportunity normally if you move through threatened squares, butdoes not provoke an attack of opportunity from the creature that struck you in the first place.
It's my general complaint repeatedly with this game: rules that are anything but certain.
I'm not going to give the rule writers credit for their lack of thoroughness/examples, otherwise you could assume if it didn't get mentioned, that was intentional. It takes all of 3 seonds to put damage and CMB together (b/c that's the best use of the feat) but only a sniff for the rule writer to not address it.