[Resettozero]

Surely, it is possible that someone is saved on faith alone: for example, someone just baptised. But this is not the general rule.

Is the general rule that one must be born an RC or convert to membership in the RCC in order to be saved from our sins and the second death?

[annalex]

Is the general rule that one must be born [a Roman Catholic] or convert to membership in the [Roman Catholic Church] in order to be saved

No, there is no such rule, nor can it be.

First, Roman Catholic Church is one particular rite of the Catholic Church; there are over a dozen others. For example, my family and I loved to worship at the Melkite Church in Sacramento; it is an ancient Catholic Church with mostly Arabic membership, they have Eastern Orthodox liturgy and practice (their priests are ordinarily married, for example) but never broke off the communion with the Pope and are Catholic. No conversion of any kind occurs when Catholics worship in different Catholic Churches. For some reason Protestants love to stress "Roman" in "Catholic", but the important thing is to be Catholic, not Catholic of Roman Rite.

Further, while Church unity is important, for your personal salvation the Holy Mysteries (or "Sacraments") of the Church are important, not external or communal aspects of your faith. While we do not have an administrative unity with the Eastern Orthodox, they have valid Sacraments and so on that level they are also Catholic.

Next, a priest is not required to baptize. Protestant baptisms are generally valid (provided they are in the Name of the Father, and of the Son, and of the Holy Ghost). So a baptized Protestant in in the state of grace from his baptism till he commits a sin. If he dies, he goes straight to heaven and he is saved; his baptism saved him.

Lastly, the conversion to the Catholic Church does not need to be formal. Often people convert when they meet Jesus at the moment of their death. We simply do not know if they do.

Often we hear: "There is no salvation outside the Catholic Church"; that is a true statement in the sense that everyone in Heaven is Catholic; but how people get there is a process quite a bit mysterious.

Do not let this complex answer lead you away from the Church though. While there is no fast rule, the only way to be sure and secure in your future salvation is to visit the local Church, inquire of the Rite of Christian Initiation of Adults (RCIA, exists in every parish) and bring the process of your conversion to completion.