I believe that the main mission of the members of the Roman Catholic Church is to serve God. This is first and foremost above anything and everything else.

I also believe that their mission is to protect the principles that the Catholic Church holds. They believe in baptism, communion, catechism, etc. They also find it very important for individuals to attend mass.

The Roman Catholic Church has a set of very defined rules and principles that are to be followed and it is also their mission to follow these guidelines on a personal level as well as helping other achieve them as well.

This question can best be answered by looking at the mission statements of the various churches that exist under the umbrella of Roman Catholicism. A look at any number of different catholic churches and their mission statements will show a great deal of similarity among them all. The Catholic church is based on tradition, it is literal in its interpretations of the Bible, and its aim is to spread its belief systems and share them with the world. Here is an example from St Charles Church:

As we pass on our Catholic heritage from one generation to the next, we are called by Jesus to be a living community of God’s people through worship, teaching, and service.

Our mission is as follows:

• To worship with one another in prayer, liturgy, and sacraments.
• To nurture our Catholic life as individuals, families, and parish community.
• To provide an authentic Catholic vision of who we are and who we are to become through our pilgrimage of faith at St. Charles.
• To personally live the Gospel of Jesus as Catholic individuals, families, and parish community.
• To continually renew our faith as we grow to understand its significance in our daily Christian life.
• To offer a program of Total Catholic Education to all members of our parish and community at large.
• To personally reach out and share our faith-filled lives within our parish and beyond.
• To care for each other as Jesus has taught us and to extend that care to others beyond our community.
• To reach out beyond our community and change the world in which we live according to the Gospel message

If you are taking a religion class, I wonder if your particular text has a specific answer you are supposed to give.  I say this, because I do not remember ever being taught that I, as a Catholic, had some specific mission other than the mission of every Christian.

As Christians, we have (or should have) a mission to follow God's word as closely as we can.  We also have a mission to spread the word of Christ by our words and by our actions.  But these are not, in my opinion, specific to Catholics.