Bombay Bazaar on Valencia at around 17th sells rose water. You can probably also find it at Haig's Delicacies on Clement and about 8th Avenue. There's also a place on Mission at 26th called Aramis, I believe.
I'm not sure if this is what you mean but Indian stores sell rose flavoring. The one on Valencia around 16th (the one with the interesting ice creams and all the Indian spices) should be open on Sunday.