Start with a very clean vase. Hold the roses next to your vase to gauge how much stem you'll need to trim. Remove any discolored outer petals and any foliage that would be below the water line; submerged leaves rot and encourage bacteria that shortens bloom life. Removing thorns is optional; doing so may shorten bloom life. If you choose to remove the thorns, carefully use a sharp blade to pare them away, working from top to bottom.
Fill a sink with cool water. Using a sharp knife or pruners, cut stems underwater at a 45-degree angle. This prevents them from sitting flat on the bottom of the vase and allows for better water absorption. If stems are especially woody, you may split them vertically an inch or so at the base so they draw more water (this may shorten bloom life). Immediately place stems in 2" of warm water (no hotter than 110 degrees). After five minutes, transfer them to a vase filled with cool water; the water level should not be above foliage. Add the included cut-flower food; use the extra pack with your first water change. To nourish flowers after the flower food is used up, refill your vase every day with a solution of one teaspoon sugar and two drops liquid bleach per gallon of fresh, cold water. Keep roses in a cool area to help them last; if you want them to open quickly, place them in full sunlight.