The other point is that just because you've had more than the minimum rest period according to the law, doesn't mean that you actually got sufficient rest. Many factors can impact on that- some of which are within the control of the airline, some of them not. EG: I know that my ability to sleep improves if I've been able to exercise that day- something difficult to do when the phone goes off at 0630 and you get back to the hotel at 1800 with an 0420 call scheduled the next day.
So I couldn't give a fig what the computer model determines to be a 'fatiguing roster', it comes down to how the crew on the day(s) of that roster feel as to whether they're fatigued or not.