This measure of our object of faith finds its power in the fact of the gospel. Christ became a servant in that Gospel so now, as a new humanity with new life, we can be proper God honoring servants. On behalf of God’s truth, Christ become a servant to those of the circumcision to authenticate and make real all of the promises given to the Jewish forefathers so therefore a Gentile believer can be a servant to those of the circumcision on behalf of God’s truth as well. Here’s how.
For God’s truth says “I will give praise to you among the Gentiles” and “Praise the Lord all you Gentiles” and “one arises from the root of Jesse who will rule over the Gentiles and the Gentiles shall hope in Him”. Therefore a Gentile believer who evidences these truths before the Jewish believers (who are prone to have strong convictions on eating and days) and before any believers (who may have convictions in different matters) then they are practically evidencing, authenticating and sounding out God’s truth summed up in the Gospel Entire.
I don’t know many Gentiles how are making Jews jealous now a day and yet Paul stated in Romans 9-11 that the Gentiles being saved was a thrust at provoking jealousy in the Jew. But how do we do that if we flaunt our freedom and never, ever, become a servant to the circumcision or the uncircumcision alike?
Christians should seriously get an appreciation for the Torah, devouring the books of Moses, the Prophets and the Writings. Christians should have no problem joining Jews for the Sabbath or celebrating the Passover festival: for in doing so with Jews the Gentiles are fulfilling the words of the Prophets and evidencing to the Jews that Yeshua (Jesus) is the Moshiach (Messiah)!
Does this mean that Gentile believers who habitually observe the Day or the Feasts is during wrong? Of course not: he or she is convinced and convicted on that position and as long as they don’t see that as a means to get higher favor from God or to ensure sanctification (or justification or glorification) then they are free to do it. I dare say some Christians have taken Sunday as the day where one must go to Church and the feasts of Easter and Christmas as hands down holy days: you can do no better than observing feasts from the actual Scriptures!
But even so, not observing them is fine if we’re not doing it with a proud idea that in our freedom we’re doing better than others and really honoring God. That preposterous thinking helps no one but ourselves and that is not to be the outworking of the Gospel in the New Humanity.
Lastly, I purposefully side-stepped Paul’s words in Corinthians I just wanted to focus on the point here in Romans but to those in Corinth (who were minded in self-wisdom and divisions) Paul would say that yes we have freedom in many things but that doesn’t mean that everything is perfectly beneficial. So it is true that a believer has the freedom to read books but that doesn’t mean that reading all books is particularly helpful. In some cases its just a waste of time. And a believer may be free to drink all wines but in some cases it’s a worthless extravagance being used merely for the purpose of advertising that a person can drink wine: it has no true benefit. But that benefit bit is the part useful for the personal edification of the believer as he or she is useful to the body of saints while Paul’s point in Romans is freedom to edify others in light of the Gospel.