Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
Sure, no problem with that, but if you don't mind easing or adding channels on one effecting the others go for it. Or you could have more then one account using different email addresses, and each would be left alone when editing the other roku.
As @Tivoburkee mentioned, you can link multiple Roku devices to a single account. The Roku account stores information about the Roku streaming devices linked to it along with the channels that are installed and purchased.
If you have a need to access different channels on each Roku device, you can link each Roku device to a different Roku account.