RoRo fun n games
Many people have shipped RoRo without incident.
BUT it is certainly NOT a safe way to secure your belongings/vehicle.
I have known people to loose insignificant items like switches or bulbs but I have also met people who have lost wheels and had the internal stripped of any value.
This is without doubt and quite obviously the worst way possible to begin your trip. Imagine arriving in Buenos Aires and being greeted with your car after somebody has smashed their way in and ripped out anything of value even of what you may think is very little value.
Apparently different ships and different routes will suffer more or less and if you opt to travel with the ship then this too is supposed to be a way of being more secure.
If the decision to not go into a container is because of cost alone then i suggest think again. If you are absolutely sure that your vehicle will not fit into a 40ftHQ then you have to opt for RoRo.
You will need to completely and thoroughly secure and seal the back of your vehicle and assume that anything you do not put into the back may well get stolen.