One of the best ways to play content from a mac or PC to a roku is to install the Plex server on the computer (https://www.plex.tv/media-server-downloads/) and use the plex client on the roku and other devices. Some of the clients and content have a fee to use, but the basic server to play your own content and the roku client are free to use.
Alternatively you can copy the content to a USB and use the roku media player, or copy to a phone or tablet and use the roku app to play it to the TV.
Thank you. I'm not sure I explained very well what I need. I don't need to get content from my cpu to the TV via Roku. I want to watch tennis matches that will play at Wimbledon.com on my TV. So I guess I want to see my web browser on the TV. I went through the ROKU menu and did not find anywhere to add a device or mirror my cpu screen. Do you know if that is possible?