Alongside his royal suzerain, Bagrat III of Imereti, Rostom fought against the expanding Ottoman Empire to which he lost parts of his principality.
By that time, Guria, a principality on Georgia's southwestern Black Sea coast, had been menaced by the resurgent Ottoman Empire, then being in war with Safavid Persia over hegemony in the Caucasus.
Rostom stood by the side of his official royal suzerain, King Bagrat III of Imereti, in his struggle against the Ottoman encroachment.
[1] In 1535, Rostom joined forces with Bagrat in an invasion of the Principality of Samtskhe, ruled by the pro-Ottoman atabag Qvarqvare III Jaqeli.
Qvarqvare died in prison, while Rostom was awarded his share of Samtskhe: Adjara and Chaneti, long sought after by the Gurieli dynasty.