Hi,
Not having a Juno DS, it's hard to say what the situation is, but Page 37 of the Juno DS88 Parameter Guide has a somewhat sketchy outline on using the keyboard with a DAW (While Composer is not, technically, a DAW, the idea is the same.)
If it didn't come with your keyboard, you can get the Parameter Guide here:
https://www.roland.com/us/support/by...wners_manuals/
Hope that helps.
David