You can determine the roof height from the format settings section in the hall settings dialog.
Location of Roof Height Setting
Select the hall where you want to change the roof height and click the right mouse button. Click the Properties line from the right click menu that opens.
Enter the hall settings.
Enter the new height value in the h3 box.
Roof height will change according to the value you entered.
Hall view before changing the roof height
Hall view after h3 is changed to 350 cm