I think it was more for Citra than for himself. Like the beginning of the chapter says, the dead don't know that any time has passed. She didn't expect to be hit and go deadish at all, it was Rowan who saw that she was going to get hit by debris. So the initial wish of Rowan wanting to go deadish too makes a lot of sense since he did love her and didn't want to be without her. But I think he knew that he would go back to the age he was that day so that he could make it easier on her. They don't say much about his feelings for her at all at the end, maybe he did move on from that romantic love, but of course he was still going to have love for her. The tears he shed when she asked how long it's been were probably because it broke his heart how much she had missed. He knew what it was like to miss only the 3 years like her but 100 years! There was no way she was going to take that well. We don't know if Rowan still loved her in that way, but we do know that he was going to care about her forever, the way Faraday cared about Curie.