Sorry that is not a rose and the whole plant/shrub looks as if it barely hanging on to life!

It looks very much like it has been starved of light, and has been grwing through another plant, ie has been growing through a conifer, has a conifer dwarfed the pot and its been searching for the light, hence the white leggy stems, julien.

Recognising that the photo is way out of focus that does not look like a rose flower to me.

It could be rosa alba semi plena from David Austen. Does it have a strong fragrance.
http://www.davidaustinroses.com/english/showrose.asp?showr=10
It has been sadly neglected but i think it is a lovely rose.

It's hard to tell as the photo is so poor, but I wonder if you had a patio rose in a pot which you put in a shed and forgot. It's been in the dark for a long time and is struggling heroically to grow.
I had a couple of amaryllis bulbs I lost and forgot about. *blush* One of them tried to flower in the box and looked quite like this.