Is roaming free in Kosovo with my European (EU) SIM card?

No. This is a very common mistake. Although Kosovo uses the Euro (€) as its official currency, it is not a member of the European Union. Therefore, the EU's "Roam Like at Home" rules do not apply. Most European carriers charge high international roaming rates here. A Cellesim Kosovo eSIM is the best way to get local data rates and avoid paying expensive fees just to use maps or check emails.