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 Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T