Each Roku has a single output that connects to the tv via plugging into an HDMI port on the tv, same as a cable box or DVD/Blu-ray player. You'll need a Roku unit for each tv.
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
If three of your TVs are smart TVs, why are you looking into Roku?
Don't get me wrong, I prefer Roku's interface to the interface of my smart TV, but what about the apps on your smart TV are the problem? What are you expecting from Roku that you don't get from those smart TVs?
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
If this post solves your problem please help others find this answer and click "Accept as Solution."