I don't know if there is any RF library that will do this, I checked
Mainframe3270 but it didn't have anything so you will probably need to create your own keyword to do this.
I found
ebcdic-to-ascii-conversions which described a command line way of converting the file, you could call the dd command with
Run and then use
Get File if you want to read the converted file. Use variables in your keyword so you can re-use it for all the files you need to convert.
Hope that helps,