First thing to do is simply restart all your network equipment. (modem, router, and extenders, etc)
Second thing you might to try is to simply try changing the "Wireless Channels" being used by the router. Login to your router or use the accompanying ISP mobile app (if applicable), and look under both the 2.4ghz and 5ghz band "Wireless Settings". Depending on which band you are connecting to (2.4ghz or 5ghz), see if a using a different channel helps. (routers will generally use Auto selection as default setting). For the 2.4ghz, try using 1, 6, or 11. If using 5ghz, try using the lower band channels 36-48 if currently using the upper band channels (149-165).
Third, depending on the model of your Roku device (whether they are single/mono band 2.4ghz devices, or dual-band 2.4ghz/5ghz devices), try using the 2.4ghz band connection. Of course, verify that your 2.4ghz band is Enabled and broadcasting. (some ISPs have disabled users 2.4ghz band on certain ISP leased routers). Using 2.4ghz should allows devices located further from router connect and maintain connections easier than 5ghz.
Since the Roku devices used to work in that room, likely just experiencing some interference or congestion. Usually just experimenting with the settings above should help resolve the issue.
If the above does not resolve issue and you have verified that both the 2.4ghz and 5ghz bands are broadcasting, could be that the router is just not working properly. Can consider either replacing router or adding an extender, an access point to your setup. These will help to extend the signal to the problem room. I like "powerline extenders", but plenty of different options out there depending on budget. Your ISP may even have options. (just don't lease any extender from a ISP. Either purchase it from them or purchase your own if they won't replace the router.) Most ISP techs will just give you them, though, if having a problem with one of their routers.
Feel free to post back with router model number, ISP (internet service provider), and the model numbers of your Roku devices if still having issues. Model numbers can be found under Settings/System/About. This may help narrow down the issues you are having.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
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