Shares of Roku (NASDAQ: ROKU) were surging today even as there was no major news out on the leading streaming distribution platform. Instead, investors seemed to be reacting to a number of smaller news items, including that Amazon was planning to launch an ad-based tier for Prime Video. As of 1:52 p.m. ET, Roku stock was up 11.6% as of 1:53 p.m. ET.