Who was Rosemary and why was she important. “I had to Jonas. That was my job” What is the Giver referring to? (page 142)

Rosemary was both the Receiver in Training and the Giver's granddaughter. She was important because she was supposed to have been the Receiver of Memories. When the Giver says that "he had to", he is referring to Rosemary's release.... something she requested, and something that he had to allow.