In that case I would go for a mixtable + two selfpowered speakersystem, where I would choose for the speakersystems with a 15" woofer built in.
A combination of a mackie mixer with f.i. JBL or EV works great and are very affordable in USA.
http://www.musiciansfriend.com/product/Live/Sound/Mixers?fg=141&sku=634221 don't have a link for JBL or EV but easy to find with google..
Then ofcourse go out and do a demo first at a place where they have arrangerkeyboards and the soundsystems!
If there's not some shop close to you having both, bring your roland with you and demo with your own keyboard!
The alternative could be a Bose PAS system but is pricy and not usable in a group unless the whole group has a Bose PAS system, while above setup allows you to use it in a group as well..
[This message has been edited by freddynl (edited 05-01-2006).]
_________________________
Keyboards/Sound Units: Kurzweil 2600S, Roland VR-760, Acces Virus C, Roland G-800, Akai AX60, Minimoog, Machine Drum, Roland R8-M, mediastation x-76