Time is a curious thing, it doesn't flow in just one direction, it flows in many.
This is evidenced with Tris's resetting of time, placing his family back through the past to what he thought should have happened. Some people like Tris, determine that time as wrong and it should be rewritten, but what they don't know is that time can't really change. It will take a different course, a new path, but the result will still be the same. He didn't know this, but he did try. He wasn't able to change their destiny: death. But death is inevitable, no one can live forever.
And when Roy looked at it that way, he could see what he had lost, but also what he had gained. By losing his ways of tempting the lovely women into his bed he had acquired a partner so devoted and so unique by any standards. And he was no less golden than he had been at seventeen. His lover and partner Edward was still as remarkable at twenty-two as he had been then: passionate and strong. He bulldozed his way through things that other's took a winding route. And in this, Roy didn't want him to change. This was the man who shared his bed, who gave him so much, and took so little, and he hoped Ed thought the same way. Ed did think the same way, and he was glad Roy had given him his freedom, if he hadn't, he would have been unhappy and oh-so unlikely to come back to Roy's arms, his bed, his heart. And lying there now, he couldn't think of a place he'd rather be than at the side of the man who had protected him, and given him everything he wanted. And when he dreamed things that scared him – images from another life, another time – Roy comforted him, soothed him until he slept again. For now they were happy and the fact that there had been another life should have scared them, but it didn't.
And in this way, we perceive people we know, but the people we know are only shadows of themselves, because of their lost lives and disconnected events makes them harder to understand, whether they know or not. In Roy and Ed's case, they know, and are content to not know what they had, but rather, are happy that they can spend the time they have left.
Because, once again time repeats itself, sometimes out of bounds, but there is one truth they all know.
Death is inevitable. Once, twice, but the third time, that's death.