[Porchdog]

Just a note on why I suggested the process I did - The finished first floor deck provides a diaphragm that ties the block walls together. That makes the base structure solid and stable. Then you don't have to worry about doing that under some temporary or low clearance structure.
You also have good structural walls to brace the jacks to lift the roof.
By finishing the roof with trusses it is also a unified structure - diaphragms around the outside and a stiff (doubled plate) perimeter. This allows you to jack it up without racking it and makes it safe on the jacks while you work under it.
You always need to account for weather while you are working - you don't want high winds shifting or lifting off your temporary roof.