Truesight and grappling

[Caliban]

You use your Base Attack Bonus, and you can use a grapple in place of a normal attack.

It sounds like another type of attack roll to me.

 

[Caliban]

In our group we have a fighter mage who likes to cast truestike and then hit with a fully power attacked sword swing. In our last adventure the monster caught on and tried to grapple the fighter mage before his blow could land. Does his true stike +20 bonus to next attack roll help with this defensive grapple roll, even though he was in fact defending and not attacking with it?

Did the monster have Improved Grab, or was this just a normal grapple attack?

If it was a normal grapple attack, it provokes an AoO, and the True Strike would apply to that.