To configure object or system roles you need to figure out which rights in the system you want specific users (or groups of users) to have.
Both types of roles are configured in the same way. You need to go to Configuration/Administration/Configuration/Basic configuration/Role editor. There you add a role and define rights it will include.
To include rights in a role, click on it and ten click "Add".
To assign an object role, you need to do two things. Go to "Roles in the organization" tab and choose a group on the left. These are groups for both objects and users. When you choose "Organization" at the top, rights in the role will apply to every object and every user. Then, on the right click "Add/Delete" to choose who will have those rights on this group.
Now, on the left choose people/groups that will have this role and on the right define which role they'll have and click "Save".
Assigning system roles is easier, because you skip the step with choosing groups. Just go to "System roles" tabs, choose a role from the left side and then choose who will have it.