Google doesn't bring up anything "new and improved". They all appear to be the same old variations on the original theme.

What is a good preservative for cut roses? Both commercial and homemade?

Google it. There are MANY recipes and they all contain sugar and acid to nourish the flowers and kill algae and mold. Some even just use Sprite or 7Up as they are acidic sugar water, perfect for the purpose.

"Secondary components found in most commercial floral food / preservatives include plant hormones which will extend vase life and improve the color and quality of cut flowers, and a wetting agent which will accelerate the cut flower's uptake of water."

copied from Floral Design Institute. So I wonder which commercial floral food has the hormone. I checked the one they sell and this is what it contains "sugar which provides nourishment for the cut flowers, a biocide which inhibits the growth of fungi and bacteria, and an acidifier, which lowers the pH of the water."... nothing about a hormone.