Hi @manishsg ,
Do you want to assign proper Security role from your Model-Driven app to large number of users?
Do you want to assign Security Role of your Model-Driven app to these large number of users automatically when you move your app from one Environment to another?
If you want to assign Security Role of your Model-Driven app to these large number of users automatically when you move your app from one Environment to another, I afraid that there is no way to achieve your needs in PowerApps currently.
The Security Role is scoped to individual Environment, which could not be migrated from one Environment to another one. If you move your app from one Environment to another one, you need to assign proper Security Role in that target Environment to these users.
Actually, it is not necessary to assign Security Role to these users one by one, you could consider create a Office 365 Group or Security Group, then add your users into this Group. Then assign proper Security Role from your Target Environment to this Group, then all members of this group would have corresponding permission to access your Model-Driven app.
More details about sharing Model-driven app to a group, please check the following article:
https://docs.microsoft.com/en-us/power-platform/admin/manage-teams#about-group-teams
Best regards,
