Today there are 8,900 Jaroush (Polish variant) / Yaroush = Ярош in Ukr, living throughout Ukraine today, most in Eastern Ukraine. Surname shows up w/some consistancy in Zhytomir, next door to Rivnenska oblast/region.
You forget that you are researching a predominantly a non-digitized world. At the local level it is best to communicate using Ukrainian. Check for Ukrainian
church near where you live, and ask priest to recommend someone to help you w/translation. Ask that cousin, who still writes to someone in village to help you???
Address to Village Mayor. Address as is.
Рівненська область 34721
Україна - Ukraine