Very few computers have video inputs, and those that do are almost always analog connections. There certainly are USB devices that add video input to a computer. I have one on my computer for copying old family VHS tapes to the computer. But since one of my computer monitors is a 43" 4K Roku TV, it really isn't necessary to send anything from a Roku player.

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But if you are referring to sending whatever the Roku is streaming to a computer over your wireless, then DBDukes offered the correct answer. Nope, can't do it without spending lots and lots of money on hardware. And I mean lots.
Dan
Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), 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.