This is an Eleven/Rose set between An Unexpected Family and Life as a Circular Paradox.
She'd asked to see it only twice since she'd been back on the TARDIS. He couldn't blame her for wanting to see it. She'd always been curious, his Rose. With more than twenty years of her husband, well, essentially of himself, teasing her about the contents of that room, he was surprised that she hadn't demanded that the TARDIS just reveal the room to her.
But Rose had respected his privacy in this matter. Which is why, nine days after reuniting with the love of his existence, the Doctor took her hand in his and led her down a darkened corridor.
"Where are we going?" Rose asked excitedly.
The Doctor pulled her to a stop in front of a nondescript door. "This, Rose Tyler," he bopped the tip of her nose with his finger, "this is the Rose room." The Rose Room was different than her old bedroom. When he slept, he slept in her bedroom. When he needed to be near her, he went to her bedroom. When he missed her, he went to her bedroom. When he needed a reason to keep going, he went to the Rose Room.
"Really?" She reached out her free hand and hesitantly touched the door. "I'm not sure I should go in there."
"What?" He jumped back in surprise. "You practically begged to see this room and now you don't want to go inside."
She gave him her tongue-in-teeth grin and darted past him into the room. Once inside, she gasped. It was like stepping outside into a garden filled with all different types of rose bushes. He had collected them from dozens of different planets. "These," he said, pointing to a bush of pink and yellow flowers, "are Tyler roses. I cultivated them for you."
"They're beautiful." Rose smiled and bent down to sniff one. "They don't smell like regular roses." She sniffed again and then looked up at him wide eyed. "Did you genetically alter these to smell like my old shampoo?"
"Yes, well," he stammered, his ears turned bright red. "I might have. Yes."
Standing up again, she kissed his cheek. "You are hopelessly romantic." Without waiting for a response, she continued to stroll through the garden until she came upon a familiar stone statue. This one was pristine, unlike the one she had last seen in the British Museum, and this one had 'my lucky pants' engraved at the bottom.
"We made two, Michelangelo and I," he explained, "when I left you as a statue outside of Rome. I told you that he taught me how to sculpt so we worked on the pair of statues. One to leave behind and one to keep here. So I would never forget my Goddess Fortuna."
A tear formed in the corner of her eye as she began walking again. Next, she came upon a wall filled with names and photographs. She recognized Nancy and Jamie from 1941, the Connellys from 1953, Chloe Webber from 2012, as well as countless others they had encountered.
But there weren't just photos from the times when they had known them. It seemed like the Doctor had followed the progression of their lives, highlighting how those people had made the world a better place. At the top of the wall was the inscription: The Stuff of Legends, making the Universe a better place one person at a time.
"After I lost you, when I wanted to stop, when I just wanted to lose hope, I'd come here." The Doctor came up behind her and wrapped an arm around her waist. "I'd remember everything that we accomplished and you would keep me fighting. After I left you and James on the beach in Norway, I stopped coming in here and I lost sight of who I am. I forgot to let you make me better."
Rose spun in his arms to face him. She reached up a hand and caressed his cheek. He leaned into her touch. "I love you, Doctor. Always have, always will."
"I love you, too." It felt so wonderful to be able to say those words to her now. Bending down, he kissed her. It wasn't their first kiss and it wasn't their last, by far. But it was what every single one of their kisses was, a promise of forever, together.