General:
* "Rosa obscura" - This is the most literal translation, using "obscura" for "dark."
* "Rosa atrata" - Using "atrata" emphasizes the blackness or darkness of the rose.
More poetic:
* "Rosa tenebris affecta" - This translates to "Rose affected by darkness," creating a more evocative image.
* "Rosa noctis" - Meaning "Rose of the night," this emphasizes the association with darkness.
Specific Colors:
* "Rosa nigra" - Specifically means "black rose."
* "Rosa purpurea" - This translates to "purple rose" and might be appropriate for a deep, dark purple rose.
Ultimately, the best translation depends on the specific context and the effect you want to achieve.