View Shared Calendar in Outlook

In the Calendar View of the Outlook (to go to "Calendar View", click the "Calendar" icon at the bottom left of the page), on the "Home" tab in the ribbon, click the Open Calendar button (in the "Manage Calendars" group).

Select "From Address Book..." in the drop-down list.
In the new window, enter the calendar display name in the search box (highlighted in yellow below)

Select the calendar that you want to see and then click OK.

You're back to the Calendar View of the Outlook. You will see that the shared calendar name has been added to one of categories in the left navigation pane. The shared calendar displays side by side with your default calendar.

You can click the left pointing arrow to overlay the room calendar and your default calendar. Navigate to whichever date that you want to know the availability of the calendar. This room calendar will remain listed under "Rooms" group in your calendar view even after you close the calendar, so you can re-open it at any time later.

When you want to add a new entry to a calendar in this overlap view, make sure the calendar you want to add to is selected before adding. Also, check the calendar listed in the bottom-left corner of the new appointment window,