Rose pedals are considered edible for humans so I am going to say they are safe for chickens too. However my chicks have had the roses I dead headed in their run and they didn't eat them. They also didn't eat lavender. They love the chard and spinach thinnings from our garden and they do eat dandelions, clover and chamomile but they seem to prefer grass (especailly grass that has seed heads) and some sort of unidentified weed we currently have in abundance.