@twardk-
Having a non-Roku smart TV with the Roku app does not turn your TV into a Roku. It only gives you access to the free ad-supported content on Roku's own service, The Roku Channel. There are literally thousands of channel apps that run on Roku, The Roku Channel is just one of them.
For access to other channels that run on Roku, like NHFS, you need a Roku account and an actual Roku device connected to one of the HDMI ports on your Samsung.
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.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X