UNITED STATES SECURITIES AND EXCHANGE COMMISSION For the year ended December 31, 2018 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Washington, D.C. 20549 Form 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 code number) 150 Winchester Circle Los Gatos, California 95032 Commission file number: 001-38211 (408) 556-9040 ROKU, INC. (Address, including zip code, and telephone number, including area code, of Registrant's ...