How many churches were there in first century Rome?

[MisterE]

In a private email exchange I had with Dr. Bock of Dallas Theological Seminary he suggested that Christians met at Christian homes in the first century and that the larger homes would be able to handle 50 to 70 believers. So, if Rome had a population of about one million people in the city, how many churches do you believe were meeting? Obviously not all one million were believers, but even if a small percent were believers, that would mean thousands of believers.

 

[follower]

"Churches in First Century Rome​

The number of churches in first-century Rome is not precisely known, but historical records suggest that there were at least 25 original parish churches, or tituli, which were the first legal churches in Rome.14 These tituli were often converted private houses where Christians initially gathered."

fwiw, I do not know nor did I search to find out what a "parish" church was.
If it was anything like roman catholic, then it was not a christian assembly.