Is there a requirement to join a Minyan?

Question

Is a person who is learning Torah in another room required to disrupt his learning in order to join a group of nine men so that they can pray in a Minyan?

The person in question comes earlier in order to learn before his own Minyan, that has for sure more than ten people. And when the nine guys come to Barchu and see that one is missing - they call the person to sit in the room, where they pray, so they would have Minyan. Of course the person in question can learn better without guys praying around him. And the question is, can he deny the request or not.

Answer 1

One source that is relevant to this issue is Rabbeinu Yonah haGerondi (13th c.) on the Rif, Berakhot 4a. There, he brings the opinion of the rabbonim of France that one need not leave one's place of learning in order to pray in a minyan:

פירשו רבני צרפת ז״ל שאפ׳ בלא עשרה היו עושין כן מפני שיותר נכון להתפלל יחידי במקום ששם קביעות התורה יומם ולילה מלהתפלל בבהכ״נ בצבור כדאמרינן אוהב הקב״ה שערים המצוינין בהלכה יותר מבתי כנסיות... אין צריך עשרה אלא למי שדרכו ללכת מביתו ללמד למקום אחר... אבל מי שלומד בביתו כל היום במקום קבוע ותורתו אמנותו אין לו ללכת לבית הכנסת אם לא ימצא עשרה מפני שנמצא מתבטל מלמודו בשעת הליכה

The rabbonim of France explained that even without ten men they [prayed in the beit midrash], since it is better to pray alone in a place designated for the study of Torah day and night than to pray in a synagogue in a congregation, as it says: "The Holy One, blessed is he, loves the gates of halakha more than the synagogues"... One only requires a minyan if it is one's custom to leave one's house [to pray] elsewhere... but one who learns in his home all day in a set place, whose learning is his occupation, needs not go to the synagogue if he is without a minyan, since he will waste time by walking there.

Note, however, that these rabbonim are speaking of one who is learning farther from the synagogue than you have described in your question, and that they focus on the obligation that the scholar has to himself, and not to a group of nine people who might require his participation. As such, I am aware that this is only a partial answer to your question, and I intend to update it, bli neder, as I find more information.

Answer 2

The Rambam in Hilchos Tefillah 9:1 seems to understand praying with a minyan as not so much of an obligation, but a good strategy:

תפילת הציבור, נשמעת תמיד; ואפילו היו בהן חטאים, אין הקדוש ברוך הוא מואס תפילתן של רבים. לפיכך צריך אדם לשתף עצמו עם הציבור, ולא יתפלל יחידי, כל זמן שיכול להתפלל בציבור. ולעולם ישכים אדם ויעריב לבית הכנסת, שאין תפילתו של אדם נשמעת בכל עת, אלא בבית הכנסת. וכל מי שיש לו בית הכנסת בעירו, ואינו נכנס לתוכה להתפלל--נקרא שכן רע

(paraphrased) The prayer of the community is always heard [by Hashem]. Therefore, a person needs* to join the congregation whenever he can. Prayer is not always heard unless you are praying with the congregation. Anyone who doesn't join the community to pray is a bad neighbor.

The Rambam does not describe it as an obligation or even a mitzvah. He couches it in terms of its beneficial effect.

I would conclude that according to the Rambam, one could not apply the principle of stopping learning to perform a mitzvah, as he will not be performing, or even facilitating, a mitzvah. You may be doing them a favor, but not a mitzvah.

This is not meant to be practical halacha, just a presentation of what I believe to be the opinion of the Rambam.

*That which the Rambam says you "need" to join the community for prayer is clear that it does not mean to imply an obligation, as the source of that line is actually a reference to that which one should say the Wayfarer's Prayer in plural, which is not even codified by the Rambam.