Agree with porkpal in that a brand new root ball in a large pot gets lost in the large amount of soil mix. Until the rose starts to put out vigorous new root growth, you need to be conservative with the water, while still giving enough, a balancing act, I know! Also, you could try some water-soluble root stimulator solution, this helps with transplant shock, and encourages root growth. You can give this every 3-4 weeks during the first growing season. I feel it's a good practice for those who grow roses in containers (or in the ground, for that matter). Also, fish emulsion fertilizer (water soluble) is a good gentle stimulant for your newly potted roses, you can give this every 2-4 weeks as well, and even give it at the same time as the root stimulator solution.
