After doing this a few times over the years, my solution has been to use rechargeable batteries. Yes, they are more expensive in the short term and they do not last as long between charges but I don't worry about corrosion.

Vinegar is good on plastic and metal components like these. If your device has rubber seals on it (waterproof), remove the seals first or use citric acid instead. Vinegar attacks rubber but citric acid does not. You can also substitute the vinegar here with citric and they both work equally well. Just be sure to remove all the citric (or vinegar) from the device to minimise future corrosion.

I can't believe you found the roku remote with batteries still in it. 🤣

These darn Roku remote mine did this now I don't keep the battery in it I could put new batteries in and two days later dead I think it's crazy how this is obviously a common issue with these remotes.