Make sure you meet the following basic requirements:
Start your iPad / iPhone and go to the following menu items:
Settings -> Accounts -> Add Account -> Exchange -> Add room credentials
If everything is ok with your connection this is confirmed by a few hooks.
Make sure you only synchronize the calendar in the next step. All other things are not needed.
Now open the Apple iOS calendar and make sure that the calendar fills up with appointments from the room.
After you have successfully connected the calendar, please navigate to the following section in the iOS settings:
Settings -> Calendar -> Sync
Please set the value to the lowest "Events 2 Weeks Ago" and one day into the future. Depending on the calendar system and iOS versions, there may be deviations in the setting options.
When you're done, please adjust the entry "Show Invitee Declines" -> off