Main lesson from this roll is it worked better than we could have expected,  given this was the first time,

We expect that software/configuration has bugs/errors and this exposed some.
There might have been some configurations that did not anticipate change in the key used ==> nothing beside rolling the KSK could have exposed that. 

There were some outages, there may have been some sites that turned off DNSSEC

and we need to get some measurements of what that long term effect was i.e. did the validation get turned back on. 

The traffic increase reported was interesting but the big picture is it was in the NOISE range, i.e. all root servers should be able to deal with such small increase. 

I have no opinion at this point when next to roll or how fast to perform that roll.