The steps are slightly different depending on your unit.
How Can I Sign out of Netflix?
If that doesn’t work either, see below for more help.

SelectSign out,Start Over,Deactivate, orReset.
Go to the Home Menu by pressing theHomebutton.
Find and highlight the Netflix app, and then press the star key on the remote.

ChooseRemove channel, and then select it again to confirm.
Roku 1
These steps are for older Roku devices released between 2008 and 2010.
Use theHomebutton to go to the Roku Home Menu.

Go toSettings>Netflix tweaks.
ChooseDeactivate this player from my Netflix account.
From the home screen within the Netflix app, pressBackon the remote.

Choose the options/gear icon on the right.
There are two ways to do this, depending on your particular situation.
This is done byunlinking the unit from your Roku account.
How Do I Log Into a Different Netflix Account?
To sign in to a different Netflix account on Roku, use the steps above to sign out.
When prompted, enter the credentials to the other Netflix account you want to use.
Another way a Netflix account could be interpreted is as a Netflixprofile.
Nothing more, nothing less.
This means signing out of Netflix doesn’t have any effect on the status of your Netflix subscription.
SeeHow to Cancel Netflixif that’s what you’re really after.
you could do it from a computer or your phone.
FAQ
There are severalfixes for when Netflix isn’t working on Roku.
Then go to the Roku Channel Store, add Netflix again, and enter with the new account.
Select a different profile, then continue to Netflix.
Netflix allows up to five watch profiles for each account.