Developer "Versatile1" has released a super useful app that allows you to access a usb drive from within Root Explorer when connected to a USB OTG cable. USB OTG add-on will automatically launch Root Explorer to the path of your USB drive when connected via USB OTG cable. This add-on saves time and makes it easier to access the files you need when on the go. While a simple app it is the perfect add-on to one of the best File manager apps on the Play Store.
This app will only set you back $1.50 and is well worth it for the added functionality.