“It's not unknown to them. They know that the apostles founded the church of Rome, just like historians do.”
Is that what historians know? What historians have you actually read on the subject?
Like many laymen, JJ is one of those Catholics who seems to get his church history, not from historians or other scholars, but from Internet popes like Karl Keating and Dave Armstrong. These are Catholics who don’t’ even study Catholic scholarship.
Part of the problem is that a lot of Catholic laymen aren’t intellectuals. So they don’t read serious historical or exegetical literature. They only read popularizers. Or watch EWTN.
Joseph Fitzmyer has written the standard Catholic commentary on Romans. It’s a monument of erudition. Here’s some of what he says about the “founding” of the Roman Church.
“In Acts 2:10 Luke lists among the ‘Jews and proselytes’ gathered in Jerusalem for the Feast of the Assembly (or Pentecost [see the NOTE on 15:24]) ‘Roman sojourners’ (pace Brown [Antioch, 104n215], epidemountes does not mean ‘residents’ [of Jerusalem]; they were rather pilgrim ‘sojourners’). Acts 6:9 also knows of a ‘Synagogue of the Freedmen’ (Libertinon), that is, of liberti, Jewish slaves who had managed to gain their freedom in the Roman world (see Sanday and Headlam, Romans, xxviii). These freedmen could actually have come from anywhere in the Roman Empire, but many of them might well have been descendants of Jerusalem Jews taken to Rome by Pompey as prisoners of war in 63 BC, who came to form a great part of the Jewish population there,” J. Fitzmyer, Romans (Doubleday 1993), 29.
“If some of the Roman sojourners in Jerusalem were among the three thousand Jews converted to Christianity according to the Lucan account (Acts 2:10-11,41), they may have formed the nucleus of the Christian community in Rome on their return there. Thus the Roman Christian community would have had its matrix in the Jewish community, possibility as early as the 30s, and thus was made up at first of Jewish Christians and God-fearing Gentiles (or even of proselytoi, Acts 2:11, also mentioned in Roman Jewish funerary inscriptions), who had associated themselves with Jews of Rome,” ibid. 29.
“The Letter to the Romans itself is actually the earliest document that attests the existence of the Roman Christian community, which Paul knows to have been in existence for ‘for many years’ (15:23),” 29.
“Much later, Eusebius tells of Peter arriving in Rome on the heels of Simon Magus to preach the gospel there in the second year of Claudius…The Catalogus Liberianus, dating from AD 354, also speaks of Peter as the founder of the Roman church, having exercised an episcopate of twenty-five years. This is undoubtedly part of a later legendary tradition tha sought to explain where Peter went when he departed Jerusalem ‘for another place’ (Acts 12:17). Eusebius’s notice encounters the difficulty that Paul in Gal 2:7-9 (written ca. 54) knows that Peter was still in Jerusalem for the so-called Council (dated ca. 49) and had apparently not yet left the eastern Mediterranean area; similarly Acts 15:6-7,” 29-30.
“A more reliable tradition associated with Paul with Peter as ‘founders’ of the Roman community, not in the sense that they first brought Christian faith there, but because both of them eventually worked there and suffered martyrdom there (or in its immediate environs), and because their mortal remains were in the possession of the Roman church (see Ignatius, Rom. 4.3; Irenaeus, Adversus Haereses 3.1.1, 3.3.2 (SC 2:11.22-23,32-33]),” ibid. 30.
“In any case, Paul never hints in Romans that he knows that Peter has worked in Rome or founded the Christian church there before his planned visit (cf. 15:20-23). If he refers indirectly to Peter as among the ‘superfine apostles’ who worked in Corinth (2 Cor 11:4-5), he says nothing like that about Rome in his letter. Hence the beginnings of the Roman Christian community remain shrouded in mystery. Compare 1 Thess 3:2-5; 1 Cor 3:5-9; and Col 1:7 and 4:12-13 for more or less clear references to founding apostles of other locales. Hence there is no reason to think that Peter spent any major portion of time in Rome before Paul wrote his letter, or that he was the founder of the Roman Church or the missionary who first brought Christianity to Rome. For it seems highly unlikely that Luke, if he knew that Peter had gone to Rome and evangelized that city, would have omitted all mention of it in Acts,” ibid. 30.
“Most likely the Christian community in Rome began not under any direct evangelization of the area, as it did in parts of the eastern Mediterranean, but through the presence of Jewish Christians and Gentiles associated with them who came to live there and went about ordinary tasks and secular duties. Slaves brought to Rome, merchants who came from other parts of the empire, and other individuals probably carried the Christian gospel there. Neither the Letter to the Romans nor the Acts of the Apostles alludes to any initial evangelization of Rome by a particular missionary, but Paul does send greetings to Andronicus and Junia, whom he recognizes as ‘my fellow countrymen’ and ‘outstanding among the apostles’ (16:7) and who may have been among such Jewish Christians who originally came from Jerusalem. The community undoubtedly also grew by the gradual immigration of Christians themselves, who traveled to the capital during the 40s via the Jewish diaspora,” ibid. 30.
Ambrosiaster tells us about Roman Christians: ‘It is evident then that there were Jews living in Rome…in the time of the apostles. Some of these Jews, who had come to believe (in Christ), passed on to the Romans (the tradition) that they should acknowledge Christ and keep the law…One ought not to be angry with the Romans, but praise their faith, because without seeing any signs of miracles and without any of the apostles they came to embrace faith in Christ, though according to a Jewish rite’ (ritu licet iudaico, a phrase found only in the cod. K; In ep. ad Romanos, prol. 2: CSEL 81:1.5-6),” ibid. 30-31.
“Suetonius, then, would have been referring to a conflict between Jews and Jewish Christians of Rome in the late 40s; the constant disturbances would apparently have been caused by Jews who opposed those who accepted Jesus as the Messiah or Lord, and who consequently differed in their interpretation of the law and threatened thereby ethnic unity and identity. These disturbances were happening so frequently (assidue tumultuantis) that they become the reason for the imperial banishment of Jews and Jewish Christians from Rome. Among the latter would have been Prisca and Aquila, who left Italy for Corinth (Acts 18:2),” ibid 31.