My bouquet was dahlias, but our Floral Event Planner suggested cushion mums for DH's boutonniere. They look very similar but not too matchy-matchy, I guess... I gave her a picture from a magazine that had little vines coming out the bottom like corkscrews, and she re-created the look with floral wire.
The groomsmen wore rossini roses (the are light pink and get darker pink toward the top) to match the roses in the bridesmaids bouquets..
Dh wore a cream rose with 2 stephanoitis to match my bouquet (his had a light blue crystal in it since his fav color is blue and I used so much pink i wanted him to have some blue )