Romans 1:8-13

Paul thanks God for the Roman saints because their faith is spoken of throughout the world. Paul says he prays for them constantly and that he desires to visit them, and experience the encouragement that their mutual faith brings.
I can find comfort and encouragement by surrounding myself with people who share my faith (mutual faith) - fellowship.
I, like Paul, am obligated to bring the gospel to all people, not to only a select group. "Be all things to all men."