I think Ducati will have to honour any genuine warranty claim no matter where the bike came from. New legislation came into force a while ago i think i remember.
It should also say on the V5 if its an import.
The sad fact is that you have to treat rockers as a consumable, even if you get it all sorted now there is still a chance they will fail again. Mileage doesnt seem to matter, my ST4 need three rockers after about 18,000 miles.
I have a bit of a problem with Ducati crap building quality myself! It was only Nelly who convinced me that i shouldnt set fire to the thing and claim on the insurance.