I would be concerned that when you water, the water flows freely from the pot. That shouldn't happen with potted plants. Potted roses sometimes have their soil contract and leave air spaces, which means that they aren't actually getting the water you apply. Water that flows freely from the bottom as you are watering is a big indication of this. Might be time to pull the rose up and see what the root ball and soil look like. I grow >150 roses in 15 gallon pots, and when I see this happen, I know I need to pull them up and re-pot. Generally, they have also showed symptoms of lack of water around the same time.
