Away from books, and this I believe, was covered in greater details in War!, but the difference between rockets and missiles is more clearly covered.
Rockets are a direct fire weapon, meaning you point it at the target, pull the trigger and hope for the best.
Missiles are an indirect fire weapon. meaning they require a sensor lock to fire. HOWEVER, they do not need a direct line to the target. SO you could fire a missile from 3 blocks over and still hit a target provided it was locked by your sensors.
And, a target lock was defined by a single success on a Sensor test.
And all this is close to how it was done in earlier versions of the game....
Now granted that was 4e, and things have changed going into 5e, but I don't recall anything different said about missile/rocket fire either way. (seems to be a 'lost' subject)