When you fire rockets, or guns, on a ship the ship tends to roll, making it difficult to get follow-on rounds on target. Unfortunately, there is no way, at the present, to completly solve this problem. Stabilizers and achoring might work, but it's not a certainty. There wa salso the problem of setting fire to the launching platform.
Modern ship-launched missiles have a booster rocket which merely flings the projectile to a safe distance before the main rocket engine ignites. Launching MLRS-type rockets from a boat is a recipe for serious ship-board-fires.