Oh Fisherlady, I'm so sorry. It just goes to show that no matter how careful we are, reproduction is risky -- so much can go wrong with both the mother and the babies, of any species.
If I'm reading the post right, it sounds like Rosie actually had a full brood cycle, or close to it. You said that she had been setting for 10-12 days when you gave her 5 mid-way eggs. Those eggs would have had another 10-12 days to go, is that right? So for her it sounds like it wasn't so much the duration of the brood, so much as her just not switching over to the next stage.
Gosh, it all seems so easy when everything goes right. I hope Rosie does better with her next clutch.