Before there were creeds to recite there were creeds to answer. The Roman church baptised by putting three questions to the candidate as they stood in the water: do you believe in God the Father almighty, do you believe in Christ Jesus his Son, do you believe in the Holy Spirit and the holy church and the resurrection of the flesh. Each answer was followed by an immersion. What we call the Old Roman Symbol is that interrogation set down as a continuous statement, and its shape still shows the joints where the questions were.
This matters for reading everything that came after it. The creed is short because a person standing in cold water cannot be asked much. It is narrative because the questions rehearsed the story of what God had done rather than the metaphysics of what God is. It carries no anathemas, no technical vocabulary and no philosophy, and the absence is not an oversight but the form working as intended.
Two fourth-century writers quote it in full and neither presents it as new. Marcellus of Ancyra, defending his orthodoxy at Rome, set it out in Greek, which is itself evidence, since the Roman church used Greek in its worship well into the third century. Rufinus of Aquileia wrote a commentary on the Latin form and compared it with the creed of his own church. Both treat it as the settled possession of Rome, which pushes its substance back at least into the second century even though no second-century manuscript of it survives.