How to launch a command or a module with mavlink/mavros?

How can I use an external offboard ros program to launch a personal module to the AUV?
I have created a module and I need to use it with multiple drones so i have to run this module in all the drones, how can I do this?
Do I need an external offboard program that send the command to all the drones or is better to run this module in another way?