The Doctor summoned another smile for Rose when she mentioned that she'd liked Donna. He'd thought she would. In fact, he thought Rose would have gotten on brilliantly with most of his companions, though perhaps not all of them. She had always been one for people. It was remarkable. No matter where or when he took her, she found a way to make friends.
He followed Rose into the complex at a polite distance, not so far back that she might feel he was trying to avoid her, but far enough that he wouldn't inadvertently crowd her, either. He didn't want to presume. The information about the amulet and a key he took in with a nod of understanding, as well as the description of the welcome kit.
"What's the amulet for?" he ventured, after a moment. "Do you mean a proper magical amulet?" Quite honestly, he didn't much care for the idea. It reminded him of the Carrionites, though he supposed Rose would have spotted any fishy business and put her foot down about it well before now if the amulet were more likely to do harm than good.