Roland's Fantom is the best workstation roland can offer. (Fantom X or the new fantom G). Only keyboards that are the same quality are korg's Triton Extreme, M3, and Yamaha's Motif ES, Motif XS.
Those are the keyboards you can play EVERYTHING on. Only thing you have to learn is how to USE the keyboard... not just play it. hehe.
Learn how to split/layer sounds, add effects and asign them to knobs or modulation wheel etc etc. You have a GREAT keyboard - just play with it.
When it comes to "sweeping" sounds... you actually don't "play them" - the keyboard does everything for you.
It's just a matter of right effects (sometimes arpeggios) triggered at the right time.
Like i said. play with the knobs and your wheels.. you'll figuire it out