Verizon is definately CDMA (The iPhone is GSM only) and I'm pretty sure US Cellular is also CDMA, at least they are here in Eastern Oregon.
In that case you are out of luck. We have Unicel here which is what I'm roaming on using a prepaid T-Mobile SIM. While they are going to get swallowed by Verizon they are supposed to keep their GSM network running for roaming income. Have you checked to see if Unicel is in your area?