First, let's define "reset". There's two kind of resets. One just restarts the device pretty much like rebooting a computer. The other is the "factory reset". I assume that's what you're speaking of when you say "reset". A factory reset will clear out all the settings and installed channels/apps. I think the device will still show up at https://my.roku.com as one of your linked devices, but I'm not sure. If you perform a factory reset you'll want to make sure you unlink the device on the website.
All that being said, resetting one device has no effect on other devices linked to the same Roku account.
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