The book of Romans was meant to establish peace between the believing Jews and Gentiles in two ways: By highlighting the mercy of God to both (salvation, justification, sanctification and righteousness), and by showing them their mutual obligations of service. Before Romans 12, Paul wrote about the importance of holy living.
Next, Paul shifted his focus to getting along in religious matters not essential to salvation (such as eating habits and the observation of holy days).
“None of us lives for ourselves alone, and none of us dies for ourselves alone... don’t put a stumbling block or obstacle in anyone’s way… Make every effort to do what leads to peace and to mutual edification (building up; growth don’t cause your brother or sister to fall.” (Romans 14:5-20)
This call to service was not a passive call. No, this was a call to actively create a community characterized by people committed to peace as well as helping each other grow, build and encourage each other. What has to happen for a community like this to grow?