A gray tuxedo jacket (Black Halo
, $440) gets a curvy update in a waist-cinching peplum style; hot pink pants (Talbots
, $119) add a jolt of festive color. "The outfit is business on top, party on the bottom," says Rossum. "I was a little hesitant because bright pants are not very forgiving, but they worked out great."
Shirt, Pink Tartan, $225. Earrings, Hearts On Fire. Bow tie, Thomas Pink. Ring, AccessoryArtists.