This has nothing to do with rooftop level.
Zoro's AP in ashura is at a level where an injured Zoro can cut Kaido. His endurance is at a level where he can, momentarily, tank Hakkai. He is well above the norm for Yonko Commanders in two separate areas when most other YC have only shown to be above the norm in one. (Katakuri - Future Sight, Marco - Regen, Jozu - endurance etc.)
Those feats don't magically disappear now that Zoro is fighting a YC. If you're being intellectually honest, you should be acknowledging that you vastly underestimated King and you should be scaling him up.