To manage roles for multiple services at a time from the Planning site, click Services, then Scheduling Matrix from the left menu.
The matrix allows you to view up to four services at once depending on your screen width. Use the arrows on the left and right of the top bar to scroll through past and upcoming services. It will only display services of the same service type, but you can switch between service types using the dropdown box next to the New button.
Below, the roles are categorized by team, which you can click to open and close. Go down the list and click Add Person to schedule a role on a given service. To delete someone from the schedule, click on their icon and select Delete. To finalize selections and send invites, you can go down the list and Send Invite per each user, or, go to Services from the left main menu, open up the service, and send invites en masse for that service. Note that you won't be able to send mass invites for all services at once from the matrix.