Roger is a lvl 12 rogue with the talent Weapon Snatcher. He is in melee fighting Badguy, both of them having a rapier, and it is Roger's turn to play.
Roger has a Dexterity of 20 and maxed his ranks in Sleight of Hand (12), so his total skill bonus is +20.
As Roger has +8/+3 BAB, he can perform two attacks. But actually he only wants to disarm his opponent, so he uses all his attacks as disarm attempts.
For the first attempt, he does the attempt at 12+5+3 = +20, opposed to his opponent's CMD (Am I right?)
For the second attempt, does he get the exact same modifier? Does he get a -5 somehow because it is his second iterative attack?
If he was using a +X weapon, would he add X to the roll? If he had other bonus to his CMB (like a flank bonus), do they get transfered to the Sleight of Hands roll?