Always cut the stems at an angle. By doing this you enlarge the hydration point.
Always remove excess leaves. By cutting the thorns off you create extra water drinking holes.
All roses, local and imported , end up at the Johannesburg flower market.
If your roses turn brown on the inside after a day or 3 since you purchased it, the reason is Botritus. This means the farm where the roses grew had an substantial amount of rain.
The farmer cuts the roses in growing stage by the time it reaches the market the heads are still closed only after a while in the growing process as the heads open up the Bontritus are visible. Remove the infected stems. Unfortunately there is no way of knowing this when you purchase the roses.
Thanks to Alsmeer Flowers @ Multiflora for these beautiful flowers
Botritus due to heavy rainfall. remember to remove these stems