What sort of "round antenna"? If it is designed for RV use, it probably already has an amplifier in it and it just needs 12v power on the coax. Need to know the make & model of antenna to be sure, though.
As JFD says, the round antennas are usually an omni-directinal type and not very effective unless the RV is located near a major metro area that has local tv stations. Directions like the Sesnar usually perform batter in RVs.