A carrier has a legal responsibility to maintain a "duty of Care" wrt its passengers and crew. If Qantas uses the properly specified lubricants and fuels, maintains the engines as agreed in the lease, it has satisfied the contract with Rolls, and with the passengers.
If Rolls exercises its responsibilities under the lease agreement, it to is in compliance with the contract with Qantas.
There is a separate "Administrative" duty to follow regulations as set forth by the Regulator (ATSB).
Here is the issue. First of all the question asked is a hypothetical one, to include injuries and fatalities. No injuries or fatalities in this incident, so what remains is twofold: Rolls duty as manufacturer, and their relationship with the Regulator, and Qantas, same.
It is a standard of Contractual Law: A Party to a contract, gaining information that has a material bearing on the terms and conditions of said contract, who does not disclose said information to the other Party, or to appropriate entities whose interest is served by said contract, commits Fraud.
It is not permissible to allow sleeping dogs to Lie. Compliant under current AD and regulations, when in possession of information that would certainly bear on existing Contracts and Laws, is not compliance.
I do not believe for a moment RR left the existing 972 on the wing, whilst "believing" the engine would explode prior to next available check.
In this instance, anyway, the likelihood of suit other than for financial losses is about nil.
The four powerplants on the 380 (972) with support and spares, is an investment of ~125 Million dollars. About one third the total cost of the aircraft. I would prefer to Lease the Power also.