Roy was using the incoming undead to do most of the grunt work most of them being mowed down by the weapons welded by the attackers. Some of them getting pasted the defenses of the attackers and started to tear them apart in a spray of blood and guts. For the most part he was acting alone not even noticing the other students figuring out their plan and such. 

Roy was moving slowly towards the soldiers using his whip to disarm any of them trying to attack him. Using the undead like a shield to protect him form the firing.