It is a shame to keep a rose from opening. But there are so many of them on the White Dawn at least -- you can see it in this post about the Big World for a Little Snail. Usually I harvest the buds when a big storm is forecast a few days out or when I'm headed out of town for a day or two. That way I really won't miss the flowers, because they will fall apart in the storm or bloom while I am gone.

Drying flowers in a big book like you did, is fun. It's a good way to deal with flowers that aren't too thick.