I’ve found that a lot of cable and network news stations can’t be subscribed through ROKU. They ask you for your ‘television provider’, and ROKU isn’t one of the possibilities.
I’ll take your word for it. When we upgraded, we of course got a smart tv. My wife also wants to keep the cable package because she has some shows she follows.
Before we upgraded, one of my adult daughters hooked a Roku device to our old tv so that she could supplement with something we didn’t get on cable. That worked fine, but she took it home with her after we upgraded. We don’t miss it.