From Gurunet:
[Middle English, rose garden, from Medieval Latin rosârium, rose garden, rosary, from Latin, rose garden, from neuter of rosârius, of roses, from rosa, rose.]

I tried making some rose-petal beads a few years ago: I'd read that their fragrance can last for years; decades, even, though fainter of course. But, as I did not have the prescribed mortar and pestle, I ran them through the food processor. Didn't work--they fell apart.