Remove foliage and thorns with a stem stripper. You can use your hands to remove the foliage, but hands and thorns don't play well together.
Cut the stems underwater. Fill a bucket or the sink with water and cut off 2 inches of stem at an angle with pruning shears or a sharp knife. Even if you want a short-stemmed arrangement, long stems are easier to work with---trim them once you've finished arranging.
Keep the stems underwater for 5 seconds then place them in a bucket half-filled with cool water. They'll stay here while you work.
Use one hand to hold the flowers and one hand to select them. Begin by arranging four roses in a square to form the center of the arrangement. Take one rose at a time and arrange them around the flowers in the center to gradually create a dome shape.
Wrap floral tape around the stems where they naturally join, about 3 to 4 inches below the flower heads. It may be easier to have a helper do this so you can hold the flowers and ensure that they keep their shape.
Place the arrangement in the container of your choice. Fill the container with water and add a few drops of bleach to prevent bacteria build-up.