Easiest thing by far is to get a 2nd Roku for other tv. To share one Roku on two tvs you'd need to run its HDMI output into an HDMI splitter (which often aren't the most reliable things in the world) then run HDMI cables to both sets. You'd be limited to watching the same thing on both sets, and likely spending as much, or nearly so, for the additional hardware as for a secnd Roku.
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well. If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X