Understand that when a rose is cut from the bush, It immediately sucks up air into the stem. This air prevents water from being drawn up into the cane. With out water the bloom dries out, wilts and doesn't open. 

You can remove this air blockage and often re-vigor a cut rose by cutting the bottom inch of the cut under water. This allows water to enter the cane and when you remove the cane from the water a tiny drop stays on the bottom preventing air from entering the cane again. You then immediately place the rose in a vase of warm water so air cannot enter.

After the roses perk up, placing them in a refrigerator for a couple of hours or overnight will condition them . this also ads to their longevity. Change the water daily cutting the ends of the canes under water each time to remove any blockage caused by bacteria, etc. You can add a little Listerine, 7-UP or bleach to the water to help also, or pick up some of those little packets of floral preserver and add to the water. The key though is to cut the stems underwater. If caught when the roses first start to wilt or droop you can often reverse the process and save them. If they have been sitting for a couple of days in this condition , nothing will help.