@Minena16 wrote: I want to know if I can put my Roku Express in my computer.
No. Computers do not have an HDMI in jack, so no external device can be connected. The only exception is if your computer has a video capture card with HDMI in. Chances of you having such a card is extremely thin, as that's not something a computer ever comes with, unless you're buying a really high end video editing system.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.