Roku stock was up 4.7 percent Monday after Apple announced at a media event that its new TV app would be available on its service. Shares had spiked to as much as 8 percent Monday in anticipation of Apple's announcement, but lost steam during the event.

Roku's jump added about $300 million to its market value, making it now worth $7.3 billion. For the last year, Roku's shares are up 109 percent.

Roku CEO Anthony Wood was spotted on Apple's campus in Cupertino, Calif. Monday, where Apple is unveiled its new streaming TV service. On face value, the service seems like it could compete with Roku's own business, which offers smart TVs and other devices that let users stream over-the-top content. But Apple confirmed its service will be available on Roku devices.

In addition to Roku, Apple's new TV app will be available on Vizio, Sony, LG and Samsung smart TVs, as well as Amazon Fire TV.

Apple has previously opted to keep its services within its own ecosystem. But recently, it's displayed more openness to working with other companies to distribute its technology. In November, for example, Apple partnered with Amazon to let Alexa control Apple Music on Echo devices. The move came after Apple's own HomePod failed to drum up as much excitement as Amazon's smart speaker.

Subscribe to CNBC on YouTube.

Watch: Roku plunges as Loop Capital cuts to sell