Hello @Jared Felsman , thank you for reaching out. I guess the following Microsoft Graph API might help you:
https://graph.microsoft.com/v1.0/users/[user-id]/appRoleAssignments
So the idea is when a user is logged in to the app, you can first call this api. From its response, you would be able to fetch the Service Principal Id labelled as resourceId in the response.
Once you have the Service Principal Id, you can make another Graph API call to get the service principal details for that corresponding service principal id by using the following Graph API:
https://graph.microsoft.com/beta/servicePrincipals/[service-principal-id]
Hope this helps.
Do let us know if this helps and if there are any more queries around this, please do let us know so that we can help you further. Also, please do not forget to accept the response as an Answer; if the above response helped in answering your query.