@Jenniet95
As @Anonymous indicated, there is no function for that.
You may wish to Submit a Feature Request for ad ratings and filters. Perhaps if there are enough submissions, Roku may give it some serious thought.
For now, Roku, Google/Android TV, and Amazon Fire TV all have ads with no filtering for them. Only Apple TV doesn't have ads.
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."