HDMI 2.1 was released in 2017 and remains the most recent version. I think Roku devices use 2.0, at least the Premiere 3920 does.
However, you might want to keep in mind that Roku has again discontinued the Premiere. (There have been a few different ones bearing that name over the years, and the Express 4K or the Express 4K+ seems to have taken the Premiere's place.)
Your question may no longer be applicable as worded. But any Roku should work just fine on your TV. So, if you worded to use another similar Roku, I'd still say it would work. You see, I have a UHD/4K, HDR Roku device attached to a 1080p TV and have no issues.
DBDukes http://www.dbdukes.com/Roku Ultra (4660) Roku Streambar (9102) Roku Streaming Stick+ (3810)