The investment bank also increased its price target on the Los Gatos, Calif., company to $185 a share from $135.
Roku shares are trading up 6.1% to $166.47. The stock has quintupled in 2019.
"Roku is one of the leading platforms for streaming TV in the U.S., via both its branded and white-label efforts (licensed operating system for TVs)," analyst Tom Forte wrote in a Sept. 4 note.
For example, one of every five U.S. TV households in 2018 had a Roku-run set, the analyst said. "As of second-quarter 2019, it boasted 30.5 million active accounts, its users consumed 9.4 billion hours of streaming video in that quarter, and its average revenue per user was $21.06," Forte said.
Forte specified four catalysts for the company: advertising, developing the Roku Channel, increasing sales of Roku TV, and international expansion.
The analyst did note risks: that competition in the over-the-top streaming-device market is "fierce" and that the company depends heavily on a "small number of content providers."