It is easy to get the car shipped (
especially from the East Coast) but the real trick is getting it done with no issues. Rotterdam is an obvious choice (
probably from Charleston) but the real issue is protecting the car. With a "roll on, roll off" you have to have complete trust in who is receiving the car. You aren't going to be there to receive the vehicle yourself and it has to go through customs.
I'd talk to someone who has experience with shipping cars for very anal owners where issues just aren't allowed to happen. I personally would talk to Alois Ruf. He regularly deals with US customer's cars being shipped over for work plus he has customers bring cars over for the road trips he puts together. He has to have a process someone he trusts a lot.
I have been exploring the idea of taking a small group of people and their cars over for a European road trip (
Targa Europa?) and one of the big details I've had trouble answering is about what it takes to get the car back into the country. I generally run a B&B exhaust and would there be an issue at customs with re-entry of a modified car? I never got a call back from the specialist at LA customs that would know exactly what is involved and I haven't tried again since then.
Also you will want insurance and seeing that the car isn't registered over there it will help to have your same US insurance company cover you. As far as I know the only US company that can cover like that is Geico. Their name stands for Government Employees Insurance Company so they cover government employees overseas. I haven't confirmed this personally and I haven't discussed this with my buddy who is a Hagerty agent to see what can be done.
European countries will want a serious assurance that once the car is in Europe the car won't be sold there. Otherwise they will want you to pay VAT.

I believe there is a time limit you can stay and avoid VAT too.
The last thing I can think of is making sure it costs the same quantity to ship it back as it did to ship it over. I'd guess that we don't ship as much to Europe as they ship to us so it could be cheaper shipping to Europe.
And if you have success I want to know about it!