How to integrate gyrometer value to get the total angular displacement

Wire.requestFrom(0b1101000,6); //Request Gyro Registers (43 - 48)
while(Wire.available() < 6);
gyroZ = Wire.read()<<8|Wire.read(); //Store last two bytes into accelZ

Why 6?.. You read 2 bytes.

.........
Gyro wont tell you how much robot is turned. You'll get the angular speed.
That means you must keep track of the time between reading to detarmine the angular change.

(Forget it ? and use the compass instead?)