As you can control apps, I'm assuming you're talking either ads or content within apps.
For ads, know that there is no functionality for rating or filtering ads. This is true of Roku, Amazon Fire TV, and Google/Android TV. Only Apple TV does not have ads within the interface. Or, at least, not overt ads. Like all services, they do push content they have designated for promotion.
For content, that would be within the app itself, if there are content ratings. Some apps do offer content ratings and filters. Some have Kids profiles. But many simply offer content, take it or leave it.
If you want to suggest filtering ads (which I suspect is the impetus for your post), you may want to submit that on the Suggest a Feature page.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
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Re: How do I remove LGBTQ stuff from my Kids seeing it?
Everyone is entitled to their own position on issues. As a grandparent, mine is that I shouldn't need to have a talk with my young grandchildren about sexual content that Roku has decided - with no option to turn it off - will now show up when I turn the TV on.
I just saw an ad for "Generation Drag" through discovery+ on The Roku Channel. So I'm contacting the channel. I'm not talking about an ad in a program I'm watching - this is on the home screen next to the inputs.
Give us an option to remove this garbage or I will be removing all Roku devices from my home.