You can move or rotate your joist takeoff by doing the following:

• Click on your measurement to select it
• Right click on the measurement and select Edit Extension / "Move/Rotate Layout and edit Joists"
• Right click on the Rotate Button and select 90 degrees.

Click on the link below for the documentation on Grid Extension (which applies to the Roll and Joist extensions). Scroll to the "Editing a Measurement's Grid Information" section.

Joist Extension Help