Welcome to the Roku Community, @MJMueller!
Thanks for reaching out. We'd love to provide further information about this to help you access your subscription account.
Please be advised that you need to install the standalone app of Paramount+ under the Streaming Store. After doing so, you'll have the option to log into your existing account and you'll have to use your Spectrum account credentials when doing so.
Here's the support article to help you: How to add apps to your Roku streaming device
We hope you find this information helpful.
Best regards,
Carly
Carly Y.
Roku Community Moderator