Hello, I am about to send my FCPX sound (of a short film) to some professsional sound people who work in Pro Tools and I wonder what the workflow is. I should use audio roles right? Do sub-roles also create separate tracks in Pro Tools?
What else should I be aware of?
Thanks

I just create new roles for each track that the sound people would want to process separately. Works great. Never used sub-roles.

How do you export it?

Check out X2Pro from Marquis Broadcast. It converts an Final Cut Pro X XML file into an AAF file. Was a bit idiosyncratic last time I received an AAF from it, but it was being upgraded fairly regularly. Not sure it still is (not a slag... I'm just not keeping up with it):

https://x2pro.net

At least worth googling around to see if it'll work for you or if it's redundant to other methods...

How do you export it?

Go to Share Master File. Click on the "Roles" tab and then pick "Audio Only as Separate Files" in the "Roles As:" pull down menu. You'll see all the roles you have assigned. The default export is wav files which is what I use. The result is as many stem files as roles the same length as your project.

I just purchased X2Pro myself last week when I naively/shockingly realized you FCPX doesn't allow you to export an AAF or OMF for professional mixing. I'm only encountering it because I've just finished my first feature, but I have to imagine a ton of people would want that functionality. Premiere lets you export an AAF. Crazy. Anyway, I'll keep folks posted if it works, but it at this point it appears to be doing so. I reached directly out to X2Pro as well to get on their radar, and see if they had any video training (because I couldn't find any from them) and they were very responsive (though they hadn't created any useful training, they pointed me to a older video that did. If anybody is interested, I'll link to that video they recommended.

There's definitely a series of steps you have to do to make sure everything comes out of your project correctly (detaching and deleting all audio from muted clips for example). Good thing is there's this running log X2Pro generates while you're exporting your AAF, that gives you info on a variety of stuff. If for example you have a file it's referencing but the original file isn't present anymore and you need to Relink the files, it will catch it and stop the AAFs export until you solve the problem.It also tells you all of the adjustments you made inside the project that are being lost on export (Compression, Voiceover Enhancement, Denoising, etc.) Attached a screenshot of that.

Update, this application ended up working great for me. I sent the AAF for approval to the Post Production Sound Facility and they reviewed it and said it was perfect. I basically followed the first half fo the video that it's creators (Marquis Broadcast) recommended and it went swimmingly. Link to the video below. It take's a little bit of cleanup on your end, and making sure your Roles are named correctly but after that you're in business. Still can't believe this functionality isn't built into FCPX!

Tutorial: How To Use X2Pro To Export Audio From FCPX & Import Into Pro Tools - YouTube