Driving the A12/E80 from cinque terre to Rome

I don’t know what a short dude trip is? Maybe trips for dwarfs?
Porto Santo Stefano or Capalbio are nice short detours along the way, if that is what you mean.

Vinci is a lovely small town with a worth-it daVinci Museum. The roads to get there are small back roads in the hills. Be prepared for cautious driving but beautiful views.

http://www.museoleonardiano.it

You could also stop in Volterra.

Oops, yes, I meant side trips. Thanks for the tips.

if you are more interested in a city, Grosseto might be worth a stop.
If you are more into smaller hill towns, then Capalbio, mentioned above, might do for you. Another nice hilltop village is Massa Marittima.
If you prefer a small town on the coast, with some great seafood, then stick with Porto Santo Stefano or Talamone.

Pitigliano is a hill town in a dramatic setting with a fascinating history which included a large Jewish community. Portions of that neighborhood are preserved and visitable including underground sections. Highly recommended and close to the coast road.