Roku Inc. topped expectations with its latest results and outlook, but shares of the media-streaming company tumbled about 15% in Thursday’s extended session.

For the current quarter, Roku ROKU models $850 million in revenue and projects it will break even on the basis of adjusted earnings before interest, taxes, depreciation and amortization (Ebitda). Analysts were looking for $829 million in revenue along with an $11 million adjusted Ebitda loss.

“We…