Hmm that's interesting. For me signing out of my account and signing back in fixes the issue every time but I don't have any smart plugs. I only have have two of the Roku light bulbs that can change to different colors via their smart home app.
I'm not sure which *shortcuts" you're referring to because I don't have that option nor do I have any smart plugs.
Even though the Roku app shows an error message as soon as I open it, I can still turn my lights on with something like the Google Home app, but I can't change or control my color profiles via the Google Home app as that is not a feature they support and so I need the actual Roku Smart Home app for that. Being able to turn the smart products on and off with a shortcut doesn't necessarily mean that there is no issue with authentication, I think the issue is within the authentication in the Roku Smart Home app itself and the MAC address of the devices linked to the Roku profile. I recall seeing somewhere that Roku changed its MAC address naming in the last update. Without knowing what kind of shortcuts you are referring to an under what parameters they operate it's very hard to know what's going on.
Anyways, signing out of my account and signing back in works for my issues and if it doesn't work for yours then it looks like there is more than one issue with the last app update which is not surprising because I'm guessing if it was a simple fix Roku would have done something by now. Sorry I couldn't be of more help, looks like it's up to Roku to figure this out.