ServiceNow works differently. Instead of thinking to restrict the user from accessing some functionality, please add the respective roles to UI action who needs to access it. It will automatically restrict access for all other users.
1. On UI action, at the bottom, please check for the roles section and add roles there.
2. Another way is, you can add gs.hasRole("role_name"); code in Condition section of Ui action. But many times this section has some script include. So better to with the first solution.
