What is it? These little green insects seem to get everywhere, and they breed like mad. As well as spoiling the look of your roses they fed on their sap and weaken them, so it's best to get rid of them as soon as you can.
Advice: The easiest way to deal with greenfly is to use a systemic insecticide like Tumblebug.Give a follow up 3 days later in case any babies have hatched. If you don't like using a chemical spray, try spraying with soapy water.