Treat it like any other leafy vegetable.. wrap it in newspaper
and put it in the closed compartment of the fridge. If not, it
might turn blackish.
If you want to go further, wet some cotton wool and secure it at
the base of the stem with aluminium foil & rubber band.
If the rose petals are abit dry when you take it out, spritz it
with fresh water & u're ready to go.