W4 6018 then FR 4437 at Fiumicino
Barcelona → Rome → Riga
Timetable, Rome time
11:55W4 6018 from Barcelona at the gate
06:00FR 4437 to Riga leaves the gate
18 h 05 apart on the timetable, overnight
FR 4437 leaves 18 h 05 after W4 6018 arrives on the timetable: more than half a day, so not a connection we count.