Mike Dundee wrote:

Who told the Romans the Gospel, the new birth?
How did they become "acquainted" with it? How do you explain this...

Romans 1:

15: So, as much as in me is, I am ready to preach the gospel to you that
are
at Rome also.

--Do you have a reading comprehension problem?
If not you would find YOUR answer in the following passage

"5Greet also the church that meets at their house.
Greet my dear friend Epenetus, who was the first
convert to Christ in the province of Asia.
6Greet Mary, who worked very hard for you.
7Greet Andronicus and Junias, my relatives who have
been in prison with me.
They are outstanding among the apostles,
and they were in Christ before I was.


--Can anyone be in Christ before Paul without knowing the Gospel?
Please answer that question --


8Greet Ampliatus, whom I love in the Lord.
9Greet Urbanus, our fellow worker in Christ, and my dear friend
Stachys.
10Greet Apelles, tested and approved in Christ.


--Apelles has been tested and opproved in Christ...
Was it with or without the Gospel? --


Greet those who belong to the household of Aristobulus.
11Greet Herodion, my relative. Greet those
in the household of Narcissus who are in the Lord.
12Greet Tryphena and Tryphosa, those women who
work hard in the Lord. Greet my dear friend Persis,
another woman who has worked very hard in the Lord.
13Greet Rufus, chosen in the Lord, and his mother,
who has been a mother to me, too.
14Greet Asyncritus, Phlegon, Hermes, Patrobas,
Hermas and the brothers with them.
15Greet Philologus, Julia, Nereus and his sister,
and Olympas and all the saints with them.
16Greet one another with a holy kiss.
All the churches of Christ send greetings.
17I urge you, brothers, to watch out for those who
cause divisions and put obstacles in your way that
are contrary to the teaching you have learned. Keep away from them.


--"The teaching you have learned" is the teaching of the Gospel
but of course your superficial reading would suggest you
otherwise --


18For such people are not serving our Lord Christ, but their own
appetites.
By smooth talk and flattery they deceive the minds of naive people.
19Everyone has heard about your obedience,

--Everyone has heard about your obedience, of course
their obedience to the Gospel of Christ...
Do you still think that the Gospel was not preached to
the Romans? --

so I am full of joy over you; but I want you to be
wise about what is good, and innocent about what is evil.
20The God of peace will soon crush Satan under your feet.
The grace of our Lord Jesus be with you.
21Timothy, my fellow worker, sends his greetings to you, as do Lucius,

Jason and Sosipater, my relatives.
22I, Tertius, who wrote down this letter, greet you in the Lord.
23Gaius, whose hospitality I and the whole church here enjoy, sends
you his greetings.
Erastus, who is the city's director of public works,
and our brother Quartus send you their greetings.[c]


Comment:
Now to come back to your question, I would just say that the Gospel
of resurrection of Christ and the life to come was preached to the
Gentiles of Rome according to Paul himself.
The bottom line is, Paul did not bring the Gospel to Rome because
some in Rome were already in Christ before Paul.

The verse you refer to may just mean

that Paul was officially
sent by God to deal with the Gentiles, that was his special
assignement, yet before taking up his assignement, someone
else did and Paul did not object to the authenticity of message
but as an OFFICIAL messenger his desire was to be in Rome to
confirm what was already known. In Rome it is about
confirmation and not a new message.