How tired the FO was or wasn't is a moot point. The captain was the one who was manipulting the controls and initially allowed the upset to occur. While the FO's alertness level could be effected by tiredness, how many newer regional FOs, based on experience level, would have taken command and overrode the captain's inputs? How many have sat there and not challenged the captain when they don't follow procedure?

I'm not throwing anyone under the bus, just pointing out that IMO experience played a larger part that sleep deprivation. When I was a newbie regional FO, I was not as forceful and direct with captains as I am now, having gotten older and been a captain myself. It was a tragic accident that occured. Hopefully politics and posturing to place blame won't obscure the important things that can come from this to make everyone else safer in the future.