Fill a clean and dry vase 3/4 full of warm water.
Add in the food packet you received with your roses. This packet has sugars in it to feed the flowers and has the chemicals that will fight bacteria from growing in the water.
Remove all leaves that might touch the water. Don't remove any thorns, as this can damage the flower's stem.
Cut rose stems diagonally while they are submerged in water. This keeps the flower stem from getting air pockets in their "straws" and helps to keep bacteria from forming. Transfer directly to your vase of water.
Change the water your roses are in every few days. When you change the water, add a new solution of plant food.