Reykjavik is 1 hour behind Rome
Best overlap: 9:00 AM to 6:00 PM in Rome is 8:00 AM to 5:00 PM in Reykjavik.
For the smoothest call, aim inside 9:00 AM to 6:00 PM in Rome, i.e. 8:00 AM to 5:00 PM in Reykjavik. Reykjavik is 1 hour behind Rome, but you'd hardly notice — 9 hours of shared hours makes this feel like working in neighbouring time zones. Note that Rome follows daylight saving while Reykjavik stays put, so the times above drift by an hour seasonally.