Hello, My name is ***** ***** I'll be assisting you. I'm sorry you're having problems.
When the remote has had battery acid corrosion on the terminals (which is what happens when the battery leaks), then the remote needs to be replaced. The acid can conduct between the contacts and short out the internals of the remote. If you wanted to "try" to clean it, then a solution of baking soda and water would need to be used as a neutralizer to clean the battery contacts in the remote and applied with a Q-tip, left to sit for an hour and then brushed off with a small metal brush.
However if that does not work, or if that's not something you're comfortable with, then the remote would need to be replaced with a brand new one (which is what I would recommend). The Roku 2 remote can be purchased at the link below for just under $10:
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