Chain. Norwegian to the people hurt and property damaged, they will in turn sue Boeing who in turn will sue Rolls Royce.
So the big winners are the lawyers I guess...
I thought the engines and the planes were purchased separately. Or are they bought as a unit for 787s?
I don't know if there are special rules for air traffic. But generally, the immediate operator (i. e. the airline in this case) would be responsible. If any of the manufacturers (or possibly a maintenance contractor) were to be responsible, the airline would simply be able to recover whatever damages they had to pay from them.
Being Rome and all... I could see a bunch of people with any sort of dings in their cars or windshield chips making claims in the near future :-)
Being an Italian born in Rome, I find your comment implying bad faith offensive.