I am trying to get the turret to tilt and roll along with the battleship as the wave hits. however i am uncertain of how to convert/add the battleship's rotation(tilt, pan, roll) into the turret rotation since the turret doesn't face the same direction as the battleship and has it's own panning.

i need some math help translating the rotation.

one option i am considering is to copy the battleship rotation entirely, and then figure out how to add the turret's panning relative to the battleship in the world axis. is this even logically correct? what math technique can I use?

Just set the turret angle to the ship angle, and then rotate it by the turret's own angle with ang_rotate.

http://manual.3dgamestudio.net/avec_ang_add.htm