Most Republic plans don’t offer roaming data. Since you happen to be on a grandfathered Republic Refund plan with your Moto G3, you do have the option of accessing roaming data. There isn’t any surprise fee for doing that per se, however, roaming data is used 18.3x faster than native data making the effective cost $274.50 per GB. Therefore, I’d suggest using it only in an emergency. Again, to be clear for others who may be reading, no surprise fee but any cell data purchased would be used much faster when roaming.
More on Republic’s refund plans here: Republic Wireless Plans 2.0: Republic Refund – Republic Help.