I mean, the Gorosei are basically Imu's commanders. So unlike Big Mom, and most other bosses of the arc, Sanji and Zoro are not exempt from actually defeating them. That argument is for Kaido, Big Mom, Shanks, Imu, Blackbeard,...the number one big bad of the group. The way we are looking at the Gorosei now is essentially the way we used to look at the likes of Cracker, Katakuri, Jack,King, Queen,....., as strong and terrifying opponents that required the SHs to power up to defeat them.
So sure, while nothing is concrete and Oda could switch up his minds later on, more than likely Zoro and Sanji each will face a Gorosei, especically considering their interations in Egghead.