Seeing how their fellow Tri-Rex was been plummeted by an unknown form of Mechanoid, the other two had decided to go full force by moving into an extreme offensive mode and their roars were an indication of its cause to do so.
Similar to the gorilla Mechanoid's shouting as it beats its own chest, the Tri-Rex roar had similar effects to the surrounding Mechanoids who were in its vicinity. All of them had some sort of debuff that caused their visions to blur out momentarily. It was not as if the entire room turned dark or they lost their connection to the sense of sight, but rather the roar had interfered with its coordination to what the user can see and what the user actually perceives.
