If all the broken spokes happened in the rear wheel, you could just replace that wheel while leaving the front in place. I'd talk to your LBS about having them hand build a wheel, something solid but not extravagant should run around $200-$300.

Rotors these days come in 2 different mounting styles, 6 bolt or centerlock, and there are adapters to use a 6 bolt rotor with a centerlock hub. There are also multiple types of freehub bodies, though most 135mm QR hubs will use a HG freehub that should work fine with your cassette.