Yes there is way but you may each need to buy a few things to to do this. What is needed is that you are able to export raw tracks so that your friend may import them, and reverse the process when you receive raw tracks back. I don't know about the specifics of the Roland unit, but what might be easiest is if you could import tracks on a PC, then either upload them or burn them into a CD-R and send them. Your friend would then either download or import the CD-R tracks into his PC, then add to, modify or what ever, and then upload or send you a new CD-R for you get back into your Roland. You would need some sort of analog or digial interface between the Roland and your PC as well as software than is compatible with your friend.

Upload and downloading is going to take a very big chunk of time itself as well as being prone to problems that chew-up even more time so keep that in mind.

The tracks can be transfered to the pc and back by a special program made by logic(I believe it is named Logic VS). So getting your tracks to the PC won't be a problem. From there it's just a matter of finding a common media or tranfer method if you both have broadband internet. Email will not work due to size limitations most email servers impose.

I know that in Digital performer you can export files in various formats, including waves and iaff files- I use these to go back and forth between DP and soundtrack- I also give my friend wave files that he can inport into his PC cubase with no problem