The Federal Trade Commission has requested additional information and documentary materials from Amazon.com Inc. AMZN, +0.91% and Roomba parent iRobot Corp. IRBT, +0.83% relating to their planned merger, according to a regulatory filing on Tuesday. The companies expect to promptly respond to the request, which will extend the waiting period imposed by the Hart-Scott-Rodino Antitrust Improvements Act until 30 days after they have complied.