I know for the vstars its 12-inch bars with some minor rerouting. Don't know 100% for the Roadstar but I am almost certain nothing over 12-inch bars will fit stock wiring on any bike. If you end up re-wiring, shoot me a PM if you have any questions. I have 16-inch bars on mine and it's not bad at all to re-wire.
Appalachian State Student Double Finance Major
2001 Vstar 650 custom
Ride to live