If you saw RS's recent Bulgaria movie, you noticed the gorgeous shots from Rose Valley. I thought it may be useful to mention that the famous annual Rose Festival begins on May 12 and concludes on June 4th. You can find a PDF version of the program in English if you click "download program" in the town's web site: https://www.kazanlak.bg/cat-470.html
For what it's worth, I also wrote about it in a blog post: http://www.flyingraconteur.com/blog/a-bulgarian-rose-by-many-other-names