Looks like rose proliferation... happened to me earlier in the year... the rose still bloomed. Nothing to worry about... read the thread below I started when it happened to me.

http://forums.gardenweb.com/discussions/3684660/does-anyone-know-whats-happening-to-my-rose-bud

Also called bullheading many of my roses are doing this at the moment. It is weather related but some of my roses are prone to doing this. For me they tend to be the densely petal packed roses. I've got one now thats two years old that does this for half the year. Hope it quits when a it is a bit older if not I'll probably get rid of it.

In my northern Illinois typical summers most of my Austins had problems. Some would bullnose others just could not open here. I still struggle to understand it as my weather seemed a lot like that of England.

It can happen in the cold and in the heat, but I noticed mine happen when there is a lack of water to the plant combined with extreme heat. (Periods of hot days with no rain while the bud is developing). Heat stress seems to be my biggest culprit, but if it rains a lot and the roses get plenty of water it seems to reduce the problem so maybe try giving them a little extra water.
Of course the rains bring cooler weather so it could just be the rest they get from the extreme heat on those rainy days that makes them return to normal, but a bit of extra watering cant hurt. However, cold can sometimes dry out roses too which is why perhaps you see this with both cold snaps and heat waves. Either way they'll return to normal when wonky weather returns to more pleasant rose-growing conditions.

My biggest culprits are Kordes roses and of my Austins only Abe Darby has this problem on occasion. Richard's Rose is one that gets this often too, it is still small but rarely has a normal bloom. I'm giving it time as I've seen it be magnificent in a garden not to far from me. Papi Delbard also does this to me in the heat of summer.