Your Roku 3 and your Roku Sticks are 5gz capable so are most likely connecting to your 5gz band of your router.
Your Roku Premieres are most likely newer and thus require the 2.4gz band of your router to operate. They will not operate on your 5gz band so your network is likely not seeing them. You need to verify that your 2.4gz band is Enabled/Broadcasting/Radio ON. If you are able to manage your router settings the standard settings are:
2.4gz Enabled, mode set to b/g/n ( Mixed), channel set between 1 and 11, and 20mhz bandwidth.
Sometimes these need some tweaking, but that should get you going.
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
