SPOILERS for the end of the series. SPOILERS I SAY-fireun
Roy watched Riza and Al play with Black Hayate and cracked the barest hint of a smile. It was excellent to have Alphonse around. The young man was a bundle of enthusiasm and good will. Riza, suffering under what was most likely an influx of suppressed hormones resulting in massive maternal tendencies, had taken to the youth immediately. She had always had a soft spot for Al-as-armor, it only made sense she would establish such a close relation with Al-as-flesh. It was good to see Al smile, and not have to imagine it. It was good to see that warm expression on Riza's face, to see the softening of those sharp eyes.
But there was a dark, hurt corner of his mind that resented the cost.
Equal exchange. Bullshit. There were some things that had no limited value, no designation of obvious worth. That cocky smile and the bedlam that inevitably followed in the wake of Edward Elric was a prime example.
It was good to have Al around, to hear him yawn when tired and yelp when he stubbed his toe, to hear his delight at the flavor of apple pastries, but none of that helped when Roy wandered back to his apartment at night. He would step over the pair of boots Ed had left there months ago, past the books that had been discarded onto whatever surface was closest to Ed when he had gotten bored of reading. He would drink left over coffee and crawl into bed, and wonder why there was so much empty space.