I did Bologna in August. It was full on unbearable - 40 degrees everyday, dashing for shade, any shade and very long siesta before emerging once the sun had gone in.
I would guess Rome would be the same, with added pollution. Things like visiting the Forum, which I thought was one of the best bits of my trip to Rome, would be completely impossible.
Rome in later September was still hot, needing a water bottle at all times, but pleasant.