Lay lavosh between 2 damp kitchen towels and let sit for 10 to 15 minutes, until lavosh is soft.
Combine cream cheese, sour cream, onion, and fennel seeds. Spoon mixture onto lavosh. Lay Swiss cheese, spinach, tomatoes, and olives overtop of mixture. Roll up lavosh tightly and cover with plastic wrap. Chill at least 4 hours but no longer than 2 days.