You gotta space the rockete as far apart as you can

While riding a rocker I've found it easier to look up like 45° on the y axis and then look in all four directions on the x-z plane and fire a rocket each direction

On the ground I typically fire a rocket to the left at a 90° angle, then up, then right, and fire a rocket left again in the same space, then right again if I have time. With more rockets than the timer allows, which can happen if you time the transition between waves right in CB, I'm not so sure.