I agree with Chuck, probably too much water. Excuse me but I'm assuming you are a novice with roses..... If tap water is used roses should be watered at the base, this will help prevent leaf scorch. The stems of the rose would benefit from pruning too. On the central bare stem I'd cut that back to just above the second leaf node (the notches on the stem). About half an inch above would be best this will encourage the stem to produce new leaves or branches. The other stems can be cut back to half an inch above the leaves.
Have you fed the rose at all?