hello99: “R’ Yitzchak Karo writes that “all of Spain follows the Rosh for all dinim and all Issur v’Heter”. This statement is strange. Sefardi minhag follows the Rif, Rambam, Ramban and Rashba much more closely then the Rosh. The Beis Yosef in his introduction famously writes that he generally follows the majority of the 3 pillars of halacha: the Rif, Rambam and Rosh. Since the Rambam writes in his hakdama to Mishna Torah that he argues on the Rif in less then 8 places, the Rosh is usually outnumbered.”
I think that R. Karo knew ????? ???? better than you. You are thinking about the way of the Shulchan Aruch. R. Karo was describing the matzav before that.
Bear in mind as well, that the Rif was in Morocco and the Rambam in Egypt, while the Rosh was in ????.