Mustafa Rumi was an Ottoman general who served the Mughal Empire under Babur.
His role in these battles as commander of rifle troops was a vital one, as it was the riflemen and the cannons under Ustad Ali Quli and Mustafa Rumi that won the day.
Babur's early relations with the Ottomans were poor because the Ottoman Sultan Selim I provided Babur's Uzbek rival Ubaydullah Khan with powerful matchlocks and cannons.
In 1513, Selim I reconciled with Babur (fearing that he would join the Safavids), dispatched Ustad Ali Quli and Mustafa Rumi, and many other Ottoman Turks, in order to assist Babur in his conquests; this particular assistance proved to be the basis of future Mughal-Ottoman relations.
[1] From them, he also adopted the tactic of using matchlocks and cannons in field (rather than only in sieges), which would give him an important advantage in India.