Sorry to hear about the issue you're running into.
To get started, I'd recommend following the steps listed here: https://support.roku.com/article/208755728-what-should-i-do-if-i-cannot-connect-to-my-home-network-or-the-internet-
If those aren't helping resolve the issue, please PM me with more information including:
1. Your Roku TV's serial number from Settings>System>About
2. The make/model of wireless router you are using
3. Any channel(s) that you experience the issue with, along with an example content title.
4. Time/date of the last occurrence of this issue.
5. Issue tracker report number, when the issue occurs (Generate this by pressing the home button 5 times, then the back button 5 times quickly on your Roku remote.)
I'll follow up with you directly to take a closer look.
Roku Community Manager