If the mapping of Role between the IdP side and the Meraki Dashboard side is consistent, this can be achieved with a single IdP.
For example, in the case of Duo Security.
* admin@example.test: Belong to Admin Group
Duo Central -> Meraki Icon/Tile -> Admin Group is mapped to ADMIN Role -> Meraki Dashboard - ADMIN Role
* user@example.test: Belong to User Group
Duo Central -> Meraki Icon/Tile -> User Group is mapped to USER Role -> Meraki Dashboard - USER Role
Note: Duo Central is the portal for Single Sign-On provided by IdP.