From Roma Termini train to Rome airport, fly to Belgrade airport, then bus to Belgrade. 4hrs 55min 111 €. From Roma Termini train to Bologna Centrale, train to Tarvisio Boscoverde, train to Villach Hbf, then train to Beograd. 19hrs 44min 193 €. From Ara Coeli- Piazza Venezia line 492 bus to Rome, bus to Florence, then bus to Belgrade. 22hrs 27min 111 €. From Ara Coeli- Piazza Venezia bus to Roma, bus to Zagreb, then bus to Belgrade. 24hrs 45min 122 €. From Rome drive to Belgrade. 12hrs 42min 235 €.