How to add a flexible database role to a database? I know there are two types of roles, one predefined (fixed), another user-defined (flexible). Here is my use case: I have a large number of AD Groups, and I am trying to map them up to a role and define permissions on that role. For example, ADGroup1, 2, 3 and 4 only should have access to database 1 tables 1, 2 and 3. To avoid re-defining the permission every single time for every single AD Group, I am trying to assign permissions to a ROLE and define the proper permissions to that single role. 

Here is the issue I get: 
For Logins, when I get properties, I get this nice "User Mappings" page that lets me define which DBs a user can have access to. But I cannot do that with a role, I cannot pick and choose databases a role can have access to. 

What should I use to achieve this? How do you combine logins? (AD groups)?

THank you very much in advance
You need to do the user/role mapping per database. 

So you create an AD group and add that as a login on the server

Within the database you define a role and set permissions for the role. Then you need to add the AD Group login as a user to the database and set them as a member of the database role. Each role can have multiple members so you can add many groups as members of the role.

You can also map the users to a server role and then add the server role as a user in the database and make that member of a database role. 

Robin Page has a simple explanation on simple talk and it's all explained in details in multiple details in many StackExchange answers