REMOVE ANY DAMAGED LEAVES FROM THE STEMS, ESPECIALLY THE ONES ON THE LOWER PART
Cut off the bottom 2cm from each rose stem end with a sharp pair of scissors. Do it every time you change the water.
Put your roses in a clean vase and ensure the stems are submerged completely for at least 10 cm. Change the water completely, at least every second day.
Add half a teaspoon of bleach to the water. It helps kill bacteria and mould.