"Nothing seems to work" ain't very helpful. Please post your current code for both parts so we can see what you've done.
In the transmitter part you should have changed from
ROT = map(ROT , 515 , 1023 , 60 , 120) ;
to the new
ROT = map(ROT , 515 , 1023 , 1200 , 1800) ;
The receiver part needed no change other than to include ServoTimer2.h. But check the output of your Serial.println(ROT) to make sure it's receiving the correct values.
When you do that what exactly is the problem you get? Is the range of movement from 1200 to 1800 correct or too much or not enough? Is the centring wrong? Which way, towards the 1200 side or 1800 side ?
Steve