On Exchange Online Room mailboxes do not share calendar information by default. You will only be able to see if the Room is busy or not. This blog describe how you enable the Room's calendar to show more information to all users.
First we need to connect to Exchange Online with PowerShell. If you don't know how to connect, please read this blog post (https://blog.ctglobalservices.com/bfa/managing-office-365-with-powershell/).
Start setting the Room calendar to show more details by default, to do so type in this PowerShell command.
Set-MailboxFolderPermission -Identity Meetingroom:\calendar -User default -AccessRights LimitedDetails
Now we are able to see more information.
To enable Room calendar to show subject of the meetings, please use this PowerShell command.
Set-CalendarProcessing -Identity Meetingroom -AddOrganizerToSubject $true -DeleteComments $false -DeleteSubject $false
Now we are able to see subjects, however this will only works on new meetings or if you update an existing meeting in the calendar.