The idea of Fasting is to understand hunger, hunger for justice, hunger for God. Thanks for the question. Rogation was not really just one day it was and still is the weekdays before the Ascension. Among farmers and herders and fruit-tree growers there is a natural and serious anxiety at this time of year. New crops are planted.
Fruit trees bloom.
A new generation of animals is born. Or a cold snap with frost that can kill newly emerged plant, fresh blossoms, and new born animals. People marched through the fields and sang psalms. Farmers asked God to protect the crops and orchard and flocks. These three days were called rogation days.