One of the secrets of Roku's success has been its expansion beyond its roots as a set top box maker (a term the company tries to avoid). To do this, Roku CEO Anthony Wood built a loyal customer following by moving the company away from only selling its own boxes, instead now licensing its software to TV makers, so they can ship screens with the company's streaming TV platform built-in. This is a much higher margin business than selling streaming hardware, and almost one-third of so-called smart TVs sold last year included Roku's software.

Roku has also developed and licensed streaming programming of its own, backed by advertising. The Roku Channel, available on all its platforms, was 2019's most popular ad-backed streaming channel, ahead of rivals Pluto TV and Crackle, according to market research firm Parks Associates. That's another business that yields higher margins than producing set top boxes.

From the article "Wall Street isn’t sure Roku can lead cord cutters to the promised land" by Aaron Pressman.