I think you said it right. Looking at images of the Vikings stadium, it looks like the roof is steeper on the steel covered North side, which makes sense since snow will be tougher to get rid of on that side because the sun won't be directly shining on it, helping to melt it.
Looks like what you are describing regarding where the roof starts on the North and South sides holds true; the South side is lower. This was surely done to promote good views of the area south of the stadium. It is unfortunate there isn't much to see in that direction. If this stadium was built in
GoSU96's beloved Inner Harbor location, it would have provided nice views of the Downtown skyline. Oh well...