A good subject is important. If you have a rose garden, can sit in a public garden or buy a fresh rose, then do try to draw from life. Your work will have much more internal 'life and a more convincing three-dimensional look. If drawing from a photograph, ensure it is a public domain image that you can legitimately use.
This photograph is by Tiffany Holmes at Stock Exchange. I chose it because it's a nice open bloom, still crisp but not too tight. The photo itself is quite clear, and I also like the simple, angled composition.
