user: Question: Which chassis had Rounds of 7, and an Entrant of Ecurie Rosier?
Columns: ['Entrant', 'Constructor', 'Chassis', 'Driver', 'Rounds']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Alfa Romeo SpA', 'Alfa Romeo', '158/50', 'Juan Manuel Fangio', '1–2, 4–7']
SQL:

assistant: SELECT "Chassis" FROM "Table" WHERE "Rounds" = '7' AND "Entrant" = 'Ecurie Rosier';