If you go to file, import audio file, then select the REX file in should drop come in fine. Thats how i do it. Failing that you can run them through the EXS24. Heres how:
* Copy the entire folder containing the rex files into a folder called sampler instruments. For example the file path on my machine will be:
JacksMac>>library>>application support>>logic>>sampler instruments.
* Once you have copied the files, open up the EXS24 sampler and select one of the rex files from the main menu.
* You will need to refresh the list before the files/list options become visible.
* Select the options tab in the top right hand side of the sampler interface
* From that menu select extract regions from recycle instrument.
* Select ok to any popup messages.
You should now find that the midi file associated with the rex file has been automatically positioned on your arrange page. You can now edit the rex file as you would for a standard midi file.