You certainly should have the "Guidelines and Rules for Judging Rose Shows" published by the ARS. It always helps to know the way the judges look at the entries.

And while at the ARS site, subscribe to the quarterly publication "Rose Exhibitor's Forum", edited by Bob Martin.

Are there any classic books on exhibiting roses that perhaps are 20, 30, or 40+ years old?

If you can find some older copies of the American Rose Annuals from the periods you want, I have a few, and they do have some articles on exhibiting. There really isn't much, Bob Martin's book is the most concise on the topic. Exhibiting is a trial-and-error kind of thing.