I visited the International Rose Test Garden yesterday, and it was heaven! The roses are coming into the first flush (bloom), and the colors were exquisite. The temps were warm and it was sunny. (Unfortunately, most of my photos were over-exposed b/c I got caught up in the real-time experience. Not such a bad thing.)
If you can get there, it's a beautiful thing to see (and it's free!). My tour guide said the peak would be between now and early July, but the roses will keep blooming and be special through September.