When I bought flowers in London, they always came with a sachet of flower food to add to the water. This helped the flowers have a longer vase life. The supermarket flowers here don't come with flower food, so I researched recipes so my flowers would last as long as possible.
There are many recipes out there but the one I have had the most success with is this:
1 litre of room temperature water
1 tablespoon white vinegar
1 tablespoon white sugar
a dash (half teaspoon) household bleach
Other tips are to remove any foliage below the water line, cut the bottom of the stems on an angle, and keep the flowers out of direct sunlight.
The roses are beautiful but you know what - they don't smell. They seem to be grown for looks rather than perfume.
Still they are beautiful.
I know 3 women my age with children the same ages as my children who have all fought their own battle with breast cancer - be grateful.