I agree, there's little information. It's still the case, I hear, that if a Roller does break down the driver rings Rolls Royce direct, who arrange for it to be whisked away in a covered vehicle so you don't see one on the back of a recovery truck.
Having said that, they are built like tanks and, too, the sort of people who own Rollers have any little niggles seen to immediately rather than put up with them. Like, sort of, the cigar lighter fails, so Rolls whips the car away and goes right over it while they're at it. Perhaps that add to the reliability legend. Plus, I suspect, owners would never admit to having bought a lemon!