Answer

Rohini Nakshatra is one of the 27 lunar nakshatras used in the Indian calendrical tradition. In Jain practice, the related observance is Rohini Vrat, a fasting day kept when Rohini Nakshatra is present after sunrise. ( drikpanchang.com)

Explanation

Traditionally, many Jains observe this vrat with fasting, prayer, and restraint. Some sources say it is especially observed by women, and the fast is concluded according to tradition with parana and sometimes udyapana. ( drikpanchang.com)

Spiritual Understanding

The purpose of such a vrat is self-discipline, purity, and devotion. In Jain dharma, the outer fast supports the inner aim of reducing attachment and living with greater संयम, or restraint. ( indiatoday.in)

Takeaway

So, in simple words: Rohini Nakshatra is the timing, and Jains who observe Rohini Vrat use that day for fasting and spiritual observance. ( drikpanchang.com)