I don't have any Win10 laptops to test currently, but I do know that I have hooked Win10 laptops to both my regular TV and my Insignia RokuTV without issue. Just about every laptop I get has Win10 installed on it until I wipe them and install different Linux OS/distros on them so I am always having to re-learn/re-fresh knowledge of Windows.
On my Roku TV, of course, you need to select the new HDMI input. (I have one named "laptop stream"). On the Win10 laptop, you need to select the Windows button (aka "super key"), then you can select either the Display Adapter or the Mobility Center if equipped. Then select "Connect Display". Then you can select "Extend" from the popup on the right hand side window of options. (Extend is the easiest, the other options offer different methods of displays - ie. showing only on TV, showing on both laptop and TV, etc).
Basically, you are just extending the display via HDMI.
On some laptops, I remember having to go into Settings and select the appropriate Display monitor. To see if Windows is detecting the second monitor, press the Windows key again, then go to Settings. (or type in Settings in the box and then select the Settings gear icon). Then select the Display. If the second monitor (your RokuTV) is not being detected, then try going into the Device Manager, selecting Display Adapters, and try updating the adapter. (You may actually have to go online and see if the Display adapter manufacturer has a new version available).
You may even have to restart your laptop after connecting the laptop to the RokuTV in order for the Windows OS to detect the second monitor (RokuTV)
In short, I can confirm that I have used Win10 laptops via HDMI with a RokuTV, but not recently, so going by memory for the above info. I do know some connected easier than others, but the more troublesome ones had their own little quirks before they would appear working. Acer, Dell, and HP all connected easily.
Maybe post back some specifics of your laptop and any screenshots to see where you are getting stuck or why yours is not working for you.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102