Sumerians might have used pulleys and levers to open and close a lotus shaped canopy, but the complexity of a stadium that size might have been risky if their ropes were not strong enough to hold up the roofing materials in high wind. Imagine, building this stadium with sticks and straw bundles! But they did use Pulleys in 1500 BC, so it is plausible, if improbable.
I think if challenged to, Leonardo Davinci might have been able to pull it off!