If your Smart TV is a Roku TV, the stick would be redundant. If it's something else, it has its own apps that are unrelated to the stick and its Roku apps. You may or may not like the way the TV works if you're used to using Roku devices. You can always connect the stick to the TV much the same way you'd connect something like a Blu-ray player to get the Roku experience on a non-Roku "smart" TV.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.