Excellent suggestion by HDMIGuy
fpefpe-
Headphone jacks are notoriously fragile. I've had them fail on tablets, cell phones and music players.
If you're still within the US 1-year warranty period, see this page for warranty and return information:
https://support.roku.com/article/208757058
Edited to add: As far as replacement remotes go, The Roku Voice Remote Pro includes a headphone jack. You can find it on the Roku site as well as local stes like Best Buy, Wal-mart, etc., andeconline stores like Amazon and eBay.
Meanwhile the Android and iOS Roku app gives you remote listening capabilites through a cell phone connected to the same home network as the Roku.