Each room ability is controlled by the player who owns the dungeon card that is that abilitys source

Attack!" When Kaiba activates any of that monster's effects, he announces "B-Buster Drake's effect!" When Kaiba Summons "Assault Wyvern", he announces "Fly in, Assault Wyvern!" Most of the time when Kaiba attacks with that monster, he announces "Slice and dice, Assault Wyvern!" When Kaiba activates that monster's effect, he announces "I use Assault Wyvern to call forth this monster!" When Kaiba Summons "Kaiser Vorse Raider", he announces "Come here, Kaiser Vorse Raider!" Most of the time when Kaiba attacks with that monster, he announces "Slash 'em, Kaiser Vorse Raider!" When Kaiba activates that monster's first effect, he announces "By destroying your monster, this card gains ATK!" (spoken as "By destroying your monster, this card gains ATK points!") When Kaiba activates that monster's second effect, he announces "By destroying this card, your monster loses ATK!" (spoken as "By destroying this card, your monster loses ATK points!") When Kaiba Summons "Krystal Dragon", he announces "Rise up

Huh, I guess this monster truly is Toadally Awesome!
The Meathook Massacre is another $30+ card thats not integral to the decks plan, so we can replace it with Drag to the Bottom