(Get-CalendarProcessing -Identity “MyAwesomeRoom”).ResourceDelegates is equal to (Get-Mailbox -Identity “MyAwesomeRoom”).GrantSendOnBehalfTo. This is good to know, because while you can do Set-Mailbox -GrantSendOnBehalfTo @{add=”user3@awesome.com”} and not kick out user1 and user2, Set-CalendarProcessing does not do this. If you try it, you get back this mess:

Cannot process argument transformation on parameter ‘ResourceDelegates’. Cannot convert the “System.Collections.Hashtable”
value of type “System.Collections.Hashtable” to type “Microsoft.Exchange.Configuration.Tasks.RecipientIdParameter[]”.

Unfortunately, I have yet to find a similar, more friendly route for adding BookInPolicy, RequestInPolicy or RequestOutOfPolicy.

All of these parameters will take an array, so you need to read in what’s there, append your new delegate(s), then write the new list to Set-CalendarProcessing:

function Add-CalendarResourceDelegate {
Param(
$roomName
, $newDelegate
)
$resourceDelegates = (Get-CalendarProcessing -Identity $roomName).ResourceDelegates
$resourceDelegates += $newDelegate
Set-CalendarProcessing -Identity $roomName -ResourceDelegates $resourceDelegates
}

function Add-CalendarBookInPolicy {
Param(
$roomName
, $newDelegate
)
$bookInPolicy = (Get-CalendarProcessing -Identity $roomName).BookInPolicy
$bookInPolicy += $newDelegate
Set-CalendarProcessing -Identity $roomName -BookInPolicy $bookInPolicy
}

Add-CalendarResourceDelegate -roomName “MyAwesomeRoom” -newDelegate user3

Removing delegates is a bit trickier; they are stored in the array as canonical names (awesome.com/Site1/Users/user1), not email or UserPrincipalName (User.One@awesome.com or user1@awesome.com). However, you just need to do (Get-Mailbox user1).Identity to get this.

function Remove-CalendarResourceDelegate {
Param(
$roomName
, $delegateToRemove
)
$resourceDelegates = (Get-CalendarProcessing -Identity $roomName).ResourceDelegates
$delegateToRemoveIdentity = (Get-Mailbox $delegateToRemove).Identity
$resourceDelegates.Remove($delegateToRemoveIdentity)
Set-CalendarProcessing -Identity $roomName -ResourceDelegates $resourceDelegates
}

And so on for BookInPolicy, RequestInPolicy and RequestOutOfPolicy.

A step closer to extending ActiveRoles Server to handle all the Set-CalendarProcessing attributes…