Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
BBC Iplayer only works on Roku devices sold in the UK, see here https://www.bbc.co.uk/iplayer/help/roku these must have either EU or UK at the end of their model number import models may not work, and/or may present issues. Roku currently only sell the Express, and Streaming Stick+ in the UK
If the premiere or any other model does launch, then it may be possible to flash UK /compataible firmware to it, however this is something that takes place automatically and you will need to factory re-set the roku and set it up again with a new account, after that it should download UK firmware, Although for now the premiere isnt available in the UK, and without the UK/EU suffix at the end of the model Iplayer will cause issues.
The easiest option would be to sell, and eiother track down a Roku 3 ( uk version) if you require an ethernet connection, or a Roku Stick+