You guys remember when Pucci attained "Made in Heaven",right?
Do you also remember the part where time sped up and Rohan was the only mangaka to actually meet his deadline. I don't know if someone already thought of this but... maybe Rohan somehow attained the arrow a got "Heaven's Door Requiem". That would explain how he was able to work regularly throughout the time acceleration, REMEMBER this theory is just for giggles (so don't go crazy over it).