I have an older Ultra and LOVE the headphone jack on the remote. I like the weight of the remote. Generally I like the remote. Just upgraded to a Roku tv and the remote that came with it is a cheap POS. The buttons stick. It’s light weight and very cheap feeling. Disappointed to say the least. Can I use the Ultra remote with the Roku tv?
Check the remote menu under settings and see if there's an option to set up a new device. If there is, then your TV supports a WiFi Direct remote. I can't say if the Ultra remote would pair, but Roku does sell a voice remote for the Roku TVs: https://www.roku.com/products/accessories/roku-tv
It will pair with roku tv, and all keys will work, but only certain models of roku tv work with headphone jack on the remote. You will only know until you try it.