First question: do you use the private listening earbud jack on the remote? If so, leaving the earbuds plugged in will drain the batteries in days. Even if you unplug them when not in use, simply using that feature will drain the batteries far faster, as it's running the audio amplifier as well as the remote itself.
If that's not the issue, send a private message to @RokuDanny-R or @RokuTannerD with your device's serial number and your Roku account email address and they can assist. Please don't post that personal information here in the forum itself.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.