Create and configure room list for outlook 2013/365

At firs verify that Windows PowerShell can run scripts:
Get-ExecutionPolicy

If the value returned is anything other than RemoteSigned, you need to run:
Set-ExecutionPolicy RemoteSigned

Connect to online Exchange server run:
$LiveCred = Get-Credential 
and type the credentials of an cloud administrator account

Then run:
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.outlook.com/powershell/ -Credential $LiveCred -Authentication Basic -AllowRedirection

After that run:
Import-PSSession $Session

When you are online check for existing Room List Distribution groups and  Room mailboxes:
Get-DistributionGroup | Where {$_.RecipientTypeDetails -eq "RoomList"} | Format-Table DisplayName,Identity,PrimarySmtpAddress
and
Get-Mailbox | Where-Object {$_.RecipientTypeDetails -eq "RoomMailbox"} | Format-Table DisplayName,Identity,PrimarySmtpAddress

Create new Room List Distribution group:
New-DistributionGroup -Name Building_nr1 -DisplayName "Buildings display name" –PrimarySmtpAddress building_nr1@yourdomain.com –RoomList

Create new Room Mailbox:
New-MailBox -UserPrincipalName room_nr1@yourdomain.com -Name "Room nr1" -Room

Add existing Room Mailboxes to Room List Distribution Group:
Add-DistributionGroupMember –Identity Building_nr1 -Member room_nr1@yourdomain.com

When you're finished using the server-side session, always disconnect Windows PowerShell by running the following command:
Remove-PSSession $Session

Detailed procedure described here:  Use Windows PowerShell in Exchange Online
and here:  Enable Room Finder with Room List Distribution Group