When she seems to lighten up a little bit he takes a cue from her and relaxes a little more as well. Although his normal demeanor is relaxed for the most part unless he's on the job. Not that his guard isn't always up on the inside, he just knows how to put on a good show.
"Rose. Pretty name." He smiles right back at her. "Derek. Derek Morgan. It's nice to meet you. I'm in this building enough to ask if you're alright since I've never seen you in here before. Or maybe we've just missed each other."