I have a Paramount plus subscription on my Apple TV, can I play this on a Roku device

Hey there, and welcome to Apple Support Communities, weirdsci.

We'd be glad to help out. Check out this link regarding Paramount Plus subscription service:

What is Paramount+?

"Which devices support the CBS app?

You'll be able to use the CBS app on: 

• iPad or iPhone
• Android phone or tablet
• Apple tvOS (4th generation and later)
• Android TV
• Fire TV or Kindle Fire tablet
• Roku
• Chromecast (via your computer or iOS/Android mobile device)

You can also stream all your CBS favorites on cbs.com." 

This link may also answer your question: How many devices can I use to stream Paramount+?

"You can use as many devices as you'd like! For example, you can stream NCIS on your Apple TV, while another family member streams FBI on their iPad. Just keep in mind that you can only use a maximum of three simultaneous streams at any time, across all Paramount+ content, regardless of the number of devices you're using."

Should you have further questions about this service, contact Paramount directly.

Cheers.