Robeson does use VIPER for the most part for fire, EMS and law. The two main towers for VIPER are Proctorville and Saint Pauls (WUNU-TV tower). The Fayetteville Spectrum tower probably also handles some of Robeson, too..
They do, however, still use 450 and 460 MHz for law, and 155.xxx MHz for fire and rescue. Proctorville has receivers, while the main transmitter site is at Saint Pauls (with receivers there, too). Robeson uses 155.160 with PL 210.7 for rescue (simulcast with VIPER). Do a search here for Robeson county scanner frequencies and plug those in. They are transmitting analog narrow-band. If you're within 25 miles of the Saint Pauls tower, you won't even need an external antenna to monitor.
Best luck..