From the Configuration cog, click on "Manage People"
Find the employee and hover over the hamburger on the right-hand side. Select "Configure Roles" 
Find the Role you wish to end and select "End Role Connection"
Select the date on which the role ended
Select "Save & Close" to save changes.
What happens next?
The role will no longer show under the employee listing
You can see previous roles under the employee profile. Click the "Edit" button in the employee profile page.
Then click the "Edit" button next to the Roles section. Here you can view Previous Roles as well as edit the current roles. Click OK when done to save the changes.
How do I create a new role?