I'm going to leave a rose and a card on the desks of my single coworkers
Why do you want to leave a rose?
I want them to feel happy when they arrive in work tomorrow
It is a sweet thought to do that for your co-workers, it is a difficult holiday to have when you are single. It will make their lives feel a little brighter.
I'm going to leave the roses to all the women. even if they are married?
That is great that you are thinking of anyone.  Just make sure that no one gets a wrong impression when you do that.