user: ### NOW ANSWER:
Question: None of the rounds has Roger Williamson as a driver.
Columns: ['Entrant', 'Constructor', 'Chassis', 'Engine', 'Tyre', 'Driver', 'Rounds']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['John Player Team Lotus', 'Lotus - Ford', '72D 72E', 'Ford Cosworth DFV 3.0 V8', 'G', 'Emerson Fittipaldi', 'All']
SQL:

assistant: SELECT "Rounds" FROM "Table" WHERE "Driver" = 'Roger Williamson';