Rosemary was admitted with a brain tumor. The mets she had were prone to bleeding, which made the surgery dangerous. She decided to go ahead anyway because while she could live with the tumor, she didn't want to live with the way it made her feel. Accepting that she may not recover from surgery, Rosemary signed a do not resuscitate order as she did not want to "lie around" attached to a life support machine.
While Rosie made it through the surgery, she did not wake up and went into cardiac arrest. Her husband was shocked that none of the staff tried to stabilize her, but Derek and Miranda gently explained that this is what she requested by signing the DNR.
Not wanting to lose his wife, Ed started chest compressions, which kept her heart beating, but did not bring her back. After he got tired and breathless, Miranda took over with the intent of stopping. However, she didn't and Derek had to step in and stopped CPR, letting her go.
She was married to Ed Bullard until her death. Before each of her surgeries, they said goodbye and then said hello again afterward. They appeared very in love and he tried to save her by giving her chest compressions, but was eventually tired and let go.