What do you mean by Romania? Romania didn't exist in the era of the HRE, it was formed by three principalities in the 1860s. I take it you mean Wallachia, but that would be hard as Wallachia was firmly in the Ottoman orbit for most of the medieval-renaissance era and the Ottomans would do everything they could to stop this happening - like vetoing a marriage in the first place.
What do you mean by Romania? Romania didn't exist in the era of the HRE, it was formed by three principalities in the 1860s. I take it you mean Wallachia, but that would be hard as Wallachia was firmly in the Ottoman orbit for most of the medieval-renaissance era and the Ottomans would do everything they could to stop this happening - like vetoing a marriage in the first place.