This is one of the features provided for each role available in the list. When you click Add Users button (), the User Role Mapping form gets opened in a popup. This form contains a list of users already assigned to the role and a feature to assign the additional users. For each user listed, there is a Delete button provided to remove the role assignment to that user.
Note that a user also can acquire permissions via Group membership. Role can be assigned to a group, and users that belongs to that group will achieve all role permissions without being assigned to role directly. Groups that have been assigned to the role is not displayed in this form, only way to see that connection is in Groups form.
Using Add new record button provided on the top of the list, you can add a user to the list to assign the selected role to the user. Add to Role popup gets displayed which shows the list of active users not yet assigned to the role. Each user in the list has a checkbox associated with it. You select the user(s) that you want to assign to the role. Search box is used to search user within the list. As soon you type the text in the search box, the list gets updated based on the entered keyword. When you have marked one or more checkbox, two buttons gets visible on the screen: Add to Role to add the selected users to the role and Cancel.