As a long-time[1] customer of Roku I am tentatively extremely pessimistic. I have always been unhappy with Roku's decision to get involved in streaming content at all, because it could potentially cut into their service-agnostic architecture. Bad enough in my mind that they had in-platform ads instead of just charging for hardware, but way worse when they are actively competing with streaming services. And now it loo…
Being a platform, Roku benefits from advertising 3 ways - by running its own ads in some apps and on home screen; by exercising carriage rights on 3p apps that show ads (getting a cut as a platform); and by building and selling audiences for targeting.
For all I know, Fox has zero interest in platforms or technology. But they are fairly sophisticated when it comes to adtech and this is purely an adtech play.