Circumcision?
Gentiles were not commanded to be circumcised under the law unless they wanted to eat the passover lamb. So there is no "we don't have to be circumcised now" as if you had to be circumcised previously. If you were an Israelite under the old covenant? Yes you had to be circumcised. If you were not under the old covenant? No you did not have to be circumcised (unless you wanted to participate fully in the passover meal).
Although you DO have to be circumcised to eat the new covenant Passiver lamb, which is Jesus Himself. You must be circumcised inwardly, in the heart. Otherwise you can't eat Christ's flesh. That is, His death won't do you much good unless your heart is circumcised.
What happens when the heart is circumcised?
Deuteronomy 30:6-8 KJV
And the Lord thy God will circumcise thine heart, and the heart of thy seed, to love the Lord thy God with all thine heart, and with all thy soul, that thou mayest live. [7] And the Lord thy God will put all these curses upon thine enemies, and on them that hate thee, which persecuted thee. [8] And thou shalt return and obey the voice of the Lord , and do all his commandments which I command thee this day.
Jeremiah 4:1-4,7 KJV
If thou wilt return, O Israel, saith the Lord , return unto me: and if thou wilt put away thine abominations out of my sight, then shalt thou not remove. [2] And thou shalt swear, The Lord liveth, in truth, in judgment, and in righteousness; and the nations shall bless themselves in him, and in him shall they glory. [3] For thus saith the Lord to the men of Judah and Jerusalem, Break up your fallow ground, and sow not among thorns. [4] Circumcise yourselves to the Lord , and take away the foreskins of your heart, ye men of Judah and inhabitants of Jerusalem: lest my fury come forth like fire, and burn that none can quench it , because of the evil of your doings. [7] The lion is come up from his thicket, and the destroyer of the Gentiles is on his way; he is gone forth from his place to make thy land desolate; and thy cities shall be laid waste, without an inhabitant.
Colossians 2:10-11 KJV
And ye are complete in him, which is the head of all principality and power: [11] In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ:
Romans 2:21-29 KJV
Thou therefore which teachest another, teachest thou not thyself? thou that preachest a man should not steal, dost thou steal? [22] Thou that sayest a man should not commit adultery, dost thou commit adultery? thou that abhorrest idols, dost thou commit sacrilege? [23] Thou that makest thy boast of the law, through breaking the law dishonourest thou God? [24] For the name of God is blasphemed among the Gentiles through you, as it is written. [25] For circumcision verily profiteth, if thou keep the law: but if thou be a breaker of the law, thy circumcision is made uncircumcision. [26] Therefore if the uncircumcision keep the righteousness of the law, shall not his uncircumcision be counted for circumcision? [27] And shall not uncircumcision which is by nature, if it fulfil the law, judge thee, who by the letter and circumcision dost transgress the law? [28] For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh: [29] But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
These passages make it abundantly clear that heart circumcision simply means God causing a person to faithfully obey His commandments out of love. Nothing in these passages, least of all the one from Romans, indicates the 4th commandment is excepted or abrogated or otherwise not a part of that obedience.