Yes, coffee grounds are good for roses, in moderation. If you pour too much into the vase it can disrupt the balance of water and air necessary to keep your flowers looking fresh. This is because coffee grounds absorb both air and water which will make the soil too dense or light for your flowers' needs.  That being said, adding a small handful sprinkled over the top of your fresh potting soil every now and then isn't going to hurt anything--and might even help. For this reason where possible try using using tea leaves instead of instant coffee beans which contain harsher chemicals that may compromise present plant tissue or leave an unfavorable scent. Tea leaves are typically larger in size which will not only give the plant more absorbable nutrients.