Can anyone bring me proofs from the Gemara that proves the world was round-and that this was known 2000+ years ago?
I have looked around and I can't seem to find any sources which prove this.
The Gemara in Avoda Zarah (41a) says:
כדור שתופש את עצמו תחת כל העולם כולו ככדור
It [The Idol] holds a ball as if to say it rules over the entire world like a ball
Tosfos explains why a ball is used as the imagery of ruling over the world (S.V K'kadur) says:
ככדור. שהעולם עגול כדאיתא בירושלמי שאלכסנדרוס מוקדון עלה למעלה עד שראה כל העולם ככדור ואת הים כקערה פי' ים אוקינוס שמקיף את כל העולם:
"Because the World is round"
Tosfos references a Yerushalmi which echoes this point:
"Alexander the Macedonian ascended on high until he saw the earth like a ball and the sea like a platter. The 'sea' refers to the ocean that encompasses the entire earth"
We see here that Chazal (as well as the Romans, as they were discussing Roman idols) had the knowledge that the world was round.
Without getting into claims of the veracity of the Zohar’s claimed authorship. The accepted traditional understanding is that it was authored by Rabbi Shimon Bar Yochai, who lived during the Tannaic period. Supposedly the Zohar makes the statement that the world is round (Though i have attempted to look for this source and have not been successful in locating it)
The fact that the earth was a sphere was well known to the Greeks (~2200 years ago), and therefore it would not be surprising that the authors of the Talmud (~1500 years ago) knew about this as well.
However, it seems that the rabbis in the Talmud did not ascribe to this view. They claimed that the earth is flat, covered by a dome, and that the sun went above the dome at night as mentioned some times in the Talmud, in Baba Batra 25b for instance:
רבי יהושע אומר עולם לקובה הוא דומה ורוח צפונית מסובבת וכיון שחמה מגעת לקרן מערבית צפונית מקפת וחוזרת אחורי כיפה
This dome was perceived as having a window in which the sun goes through at dusk / dawn, as the targum on Kohelet states:
אזיל כל סטר דרומא ביממא ומחזר לסטר ציפונא בליליא אורח תהומא מחזר מחזר ואזיל לרוח עיבר דרומא בתקופת ניסן ותמוז ועל סחרנוהי תיב לרוח עיבר ציפונא בתקופת תשרי וטבת נפיק מחרכי מדינחא בצפרא ואעיל לחרכי מערבא בשמשא
This idea even made it's way into the modern day prayer book:
הפותח בכל יום דלתות שערי מזרח ובוקע חלוני רקיע מוציא חמה ממקומה ולבנה ממכון שבתה
So, the proof you are looking for does not really exist, since the rabbis of the talmud explicitly dismissed the Greek model. The fact that subsequent generations of rabbis interpreted the Talmud to refer to a spherical earth as in the answer above, does not actually say anything about the view of the rabbis themselves, which as shown, did not support a spherical earth.
Addendum: Just found that Natan Slifkin has written quite a long piece on the subject, bringing many additional sources to support the claim made in this answer: The Sun's Path At Night.