Roller Fan?
The Rolls engines are nearly a tonne heavier than the GE's. While the Vmcg is lower, their performance in the climb above mach transition is considerably less than the GE's. They take 5 minutes to warm up (3 for the GE), so for short taxi times like LA for 24L, the warm up time can be a limitation for departure (if the cabin crew are fast enough). The residual thrust is less (so on flare I always retard the levers at 30ft for the Rolls) c.f. 50 ft for the GE's, and as it is company policy to shut down 2 engines on arrival after the mandatory cool down period, the Rolls always requires more than idle thrust to keep the aircraft moving. Plus they whine like a bunch of Poms on a Seven's holiday.
Give me GE's anyday!