Yes.
The Roku is just another device. It doesn’t interfere with any other devices or services. For example, it’s possible to have satellite TV, cable TV, over-the-air TV, Roku, FireTV, Blu-Ray, PlayStation and more all connected to a TV and switch back and forth between them as frequently as you wish.
In general, there is no need to unplug anything, unless you TV has very few inputs. In that case, you can unplug or get a switch (or AVR) to use as many devices as you wish.
Banned but back. Because why not?