No, it's not the roof actually. Have a look from this cam. Those steel 'beams' leaning towards the pitch are at ground level.
Yep that's the roof. It will all form the cable tensioning system, it's done at ground level then lifted upwards into position. All the stuff laid out on the ground in-front of the North stand are parts of the roof yet to be fitted. This is a different design roof but this is the principle.