I had the same sad feeling, when visiting the place. As I came to live in Rueil Malmaison recently, I met the present owner of the Josephine's house. Unfortunately the state does not care much about the state of the gardens or even Josephine's house. I would like to restore this beauty so at the present moment I thinking of a business project that would allow to finance the works
Tatiana

There is a great deal of very interesting controversy on this topic. Probably because a lot of it is speculation. However, many people believe it's unlikely that Josephine had a highly decorative layout, like we think of at rose gardens like L'Hay les Roses or Bagatelle. The consensus seems to be that in those days the rose was used as a decorative shrub in mixed plantings by garden architects like Blaikie, or in the Potager for cutting and herbal/medicinal reasons.

However, Josephine also lived in the days when botanical collection was at its heyday so another possibility is that her roses were grouped as plants are in systemic gardens, by family or similar characteristics. I like this theory. It's also likely that some of them would have been sheltered in her extensive green houses. They were rare, collectors items, after all.

Even though I like this theory, I've found source that actually claims to show a rare (and not very detailed) layout of her gardens. The Book called "History and Development of the Modern Rose" shows a plan by E. Touret and says that "the roses were situated on the main axis in long rectangular beds". I'm sorry that I've misplaced the author's name; will edit this if I find it, but you should be able to find it by name.

Also, I have not found a definitive list of roses that Josephine grew. Redoute painted many of her roses but also roses from other sources. Almost 100 years after her death, the designer of L'Hay and others put together a list of 197 varieties that they believed she grew, in part from the Redoute prints, and published them in 1912. The book mentioned above has that list, too; which may be as close as you can get.

The book also implies that the gardens were restored from the same Touret drawing. I can tell you that the old rose garden at Malmaison today looks nothing like the drawing in the book.

Let me know how this plan is progressing!

Sorry that I cannot answer it myself, but perhaps you can ask André Joyaux at rosagallica@free.fr