First of all, you must realize there is no word in the ancient Greek for Sabbath.....primarily, as it was never celebrated. Consequently the Hebrew, Shabbat or Shabbaton (special Sabbath) is translated Sabbatwn in [Matthew 28:1][Mark 16:2][Luke 24:1][Acts 20:6-7] and [1 Corinthians 16:2].
Since "Sabbatwn" is a borrowed Hebrew term identifying certain special days of the Feasts, we know this term refers to one of the seven weekly Sabbaths between Passover and Pentecost during the counting of the Omer. The Greek word "mia" as in "Mia Twn Sabbatwn" does not mean first....it means one. If the scripture were speaking of the "First Day" it would say....."Protos Hemera".....hemera meaning Greek for "day".....protos for "first". As indicated in my earlier response to you the word "day" is Italicized and does not appear in any manuscript. It was added by those with a Sunday observance agenda.
So, by the Holy Spirit inspiring the words "mia twn Sabbatwn", it is very clear that Our Saviour's resurrection took place on a day that was both a weekly Shabbat....as well as an annual Shabbaton.....one of the weekly Sabbaths from Passover to Pentecost...obviously, the first one. That is why many translations show "First of the Sabbaths". To translate this term as "First Day of the Week" not only changes the primary meaning of the word "mia" but it ignores the fact that the Hebrew term Shabbaton even exists in the Greek text as Sabbatwn.
The Sabbath is mentioned 126 times in the Old Testament ....62 times in the New. The words "First Day of the Week" are mentioned eight times in the King James Bible, each time an incorrect translation.....and not once with a sacred intent. Five of these times are the "women visiting the tomb"[Matthew 28:1; Mark 16:2; Mark 16:9; Luke 24:1; and John 20:1]. One of them show the disciples assembled "For Fear of the Jews" [John 20:19]. Another shows an after Sabbath (Havdalah) meal [Acts 20:7]....notice the lights are on. The last one is simply a collection for the poor in Jerusalem [1 Corinthians 16:2].
You may sincerely believe that Sunday worship is not a Roman tradition....but you are very wrong. It is the basis of their entire religious system....Sun worship. unfortunately, they have convinced much of main stream Christianity of the legitimacy of this false system but if one desires to seek the truth in all things....it is not difficult to uncover.
There is a problem with your accusation that the Roman Catholic church came up with worship on the first day of the week. Christians were worshipping on that day long before the Catholic church came into existence.