From Roma Termini train to Rome airport, fly to Belgrade airport, then bus to Belgrade. 4hrs 55min 112 €. From Roma Termini train to Bologna Centrale, train to Tarvisio Boscoverde, train to Villach Hbf, then train to Beograd. 19hrs 44min 194 €. From Ara Coeli- Piazza Venezia line 492 bus to Rome, bus to Florence, then bus to Belgrade. 22hrs 33min 104 €. From Ara Coeli- Piazza Venezia bus to Roma, bus to Zagreb, then bus to Belgrade. 24hrs 43min 123 €. From Rome drive to Belgrade. 12hrs 42min 236 €.