This is not entirely correct. You'll rarely hear a Roman Catholic talk about being saved as if the event has occurred. Instead, salvation is more...shall we say...of a process than Baptists might understand. Baptism is the act of ushering one into the communion with the Holy Church, but it is not "salvation" in and of itself. Salvation, for Roman Catholics, doesn't occur until after the end of one's life. Only at that point is one "saved" (again they wouldn't likely use that term.)
One of the massive differences soteriologically between Baptists (et al) and Roman Catholics is indeed our understandings of the nature of salvation. At the core of Roman Catholic soteriology are the sacraments; Baptists are not sacramentalists. For Roman Catholics, salvation is something that is maintained so long as someone remains in communion with the Holy Church (their Church.) It begins with infant baptism (or adult baptism...which can be done by immersion btw) which ushers the child under the provisional sacrament of the Church. Then, following confirmation, the regular participation in the Eucharistic service (where Communion, or the Eucharist) is offered and consumed is part of this. The other sacraments work in as well. If one deviates, massively, from the teachings of the Church and walks away from regular participation in the sacraments, they are considered apostate. If you die in this state, your mortal sins can send you to Hell.
Anyways, it isn't accurate to say that "baptism=salvation" for Roman Catholics. It doesn't provide this completely.
Ultimately we have to ask ourselves, once we clear away the false understandings about other forms of Christianity, what do we do with the massive segment of people who have lived and died faithfully in the Roman Catholic Church who didn't have another option? For the millions upon millions of people who lived between about CE 1000 and 1550 there wasn't really another option. How then should we understand their mortal state? Is God so crass that He sends faithful, Jesus proclaiming people to Hell simply because of a corrupt ecclesiastical situation?