Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
Unless your PS4 has an HDMI input port like a TV does, which it can pass through to the TV, then you can't do that.
I assume your problem is that you don't have another available HDMI port on your TV? You can purchase an HDMI switch and use it to control which input you view on your TV. Hook it up as below (substitute your PS4 for DIRECTV):
