One thing that is easily overlooked is that the Roku can only apply parental controls to the programming originating with Roku, i.e. The Roku Channel.
For parental limits from other sources, some have such controls and others don't. You'll have to try to find them for each individual source. You may have to log into your account on their website to find such controls.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T