The Los Gatos, Calif., company reported a net loss of 22 cents per share compared with 9 cents in the year-earlier quarter. The latest figure compared with the FactSet-derived analyst consensus estimate of 28 cents.
Revenue of $260.9 million, a 50% year over year increase from $173.4 million. Analysts were looking for $256.4 million.
Roku shares dropped 14% to $121.27 after hours.
The company reported average revenue per user of $22.58, topping analyst estimates, while streaming hours rose 68% to 10.3 billion. Roku added 1.7 million active accounts sequentially, bringing its total to 32.3 million.
Roku also increased its revenue and gross profit guidance for 2019.
The midpoint of its revenue outlook is now $1.11 billion, representing 49% year-over-year growth. That's up from its previous outlook of 46%.
Meanwhile, its gross profit is expected to be $492 million at its midpoint, up from its previous view of $485 million.
The streaming hardware provider's stock has risen nearly 40% since the August release of its second-quarter earnings, leading Rosenblatt Securities on Tuesday to issue a bullish note on the company.
"We've characterized Roku as a runaway train given its significant OTT [over the top] TV lead in branding and U.S. household penetration," said Rosenblatt analyst Mark Zgutowicz.