Depends how fragrant they are. Potpourri is the obvious choice, but there are only so many bowls you can have sitting around the house before people start to think you have gone mad.

You could use them in any cleaning concoctions. I make a surface spray by soaking either citrus rinds, lavender or rose petals in white vinegar and mixing it with half water and a few drops of dish washing liquid in a spray bottle. Works a treat and for harder to clean things like the bath and oven, I just add a bit of baking soda to the surface.

Or melt down plain soap and add ground petals to it. Make it into rose water, great for re hydrating your skin in a mister.

You can eat them if you really want. Make rose petal syrup out of them or real turkish delight. There are heaps of other Middle Eastern deserts that use rose water.

And I haven't even started on the rose hips yet!

Good luck