I am not sure if it the back button or the back directional button on the Roku3 remote, but when I rewind, it enables Closed Captioning. I need to hit the * and choose disable CC.
-MattMatt13
This was documented in another post as well. Mine does the same thing, but turns off after about 10 seconds. As the other post suggested, this might be a roku feature as Netflix app does the same thing.
After using it, it is rather nice tool if you missed what was heard and wanted to replay with CC.
I noticed it only turns on when directional pad left is pressed one time. If left is pressed multiple times it will not enable CC.
I agree… It’s a Roku setting. Like guck11 says, it’s a nice feature if you couldn’t hear the previous dialog spoken. And like MattMan suggested, just hit the * button on the remote to choose the setting you want. If you disable, it doesn’t seem to do it anymore.
Interesting thing here @TabloSupport, I see the same thing with Amazon also. Hit the left arrow and CC comes on.
Hm - weird. I’ve looped our developer in on this and we’ll take a look. Thanks, all!
It’s a common behaviour amongst Roku channels because most of us use the same Video Player “package” available on the Roku.
As @Diligent said you can disable it by clicking “*” on your remote while playing a video, then select “Disable closed captioning”; the reason behind the initial behaviour is that the third item from the closed captioning menu was selected (maybe by default?): “Enable closed captioning during instant replay”.
Ok.. I did some checking and I think I found the solution. There is a global setting in Roku that causes this. Go to Settings -> Captions -> Captions mode. There you will see the three options. "Instant Replay" was checked on mine by default. Check "Off". That should clear it up.
After making that change, I couldn't duplicate the problem again.
Ok, the left arrow is Instant Replay and that is what closed caption appears to be set to by default.
Go into settings/Captions and change it to off 
@Jestep Thanks… I found it too, and was editing my original post during your post! LOL… 
Actually seems like a cool feature. I was watching a show tonight and rewound 3 times to try to figure out what one character was saying and still didn’t hear it… had to guess. But I don’t have a Roku, so maybe it is uber annoying IRL.