The key? Color gradation. The colors range from light to dark. There's no strong contrast of vibrant red and vibrant purples and oranges. There is a smooth gradation of color, with one dark shade that "pops" as an accent.
Photos: Lucas Allen
Also a good find: http://www.freshroses.com. Recommended by Real Simple's article, and other respectable publications.
x-posted from LBB.