Yes, 4K movies and TV shows can be viewed on any Roku® streaming player or Roku TV™ that supports 4K. Be sure to check on how to setup your Roku Streaming player for 4K.
The Roku Channel Store
How do I find 4K movies and TV shows?
In addition to searching the Roku Channel Store on your Roku device or the Roku website to find 4k movies and TV shows, you can browse the 4K Spotlight channel.