The rotors we install at Jensen Sprinkler are largely the  Rain Bird© 3500 or 5000 series rotors. Quite conveniently, these heads adjust the same way. 

How far the sprinkler head throws out is limited by the style of head and the nozzle that was installed, but it can be adjusted with a small flat-blade screwdriver. This is called adjusting the radius of your sprinkler head. The radius adjustment screw is found on the top of the sprinkler head, closer to the nozzle. If your sprinkler isn't in operation you can tell which way the nozzle is facing by the arrow on the top of the head. Turning the screw clockwise decreases the distance the sprinkler waters, turning it counter-clockwise will increase the distance of throw.  Here is a short video from Rain Bird© that you should find helpful: