This object is only available in the Ci Essential Library for Australian and New Zealand Select (SSA) Customers.
Essential Library can be downloaded from https://myci.centralinnovation.com
1. Draw a single-plane roof with a roof pitch of 0 degrees
2. Select the roof then go to Design > Design Extras > Accessories > Roof Accessories....
Please note you may need to install the ARCHICAD goodies https://www.graphisoft.com/downloads/goodies/
3. Select the desired settings then click ok.
Note the Roof Pivot Line will set the origin of the ceiling grid.