Question
My knockoff roses are infested with Japanese beetles. Can a solution of detergent and water sprayed on them get rid of them and prevent them from returning, without injury to the blooms?  Illinois (central) location

Answer
Spraying the beetles with soap and water will only make the beetles nice and clean. Because they have backs that are hard shelled, nothing will penetrate them. Hand picking them off in the early morning when they are sleepy, is the only organic way to keep them under control. If you have a particular rose that is very important to you and you don't want it damaged, then wrap it in bridal veil type material. This prevents Japanese beetle getting at it and they won't be around forever. They have a set time that they are active in your area.
Here is an excellent article on Japanese beetles.
http://gardening.about.com/od/gardenproblems/a/Japanese_Beetle.htm