How will you get past the opening lintels seeing as they are 3m tall? How will you go on once more than half the roof space is occupied?
Before half the trusses are on, put the rest up on the wall plate resting on the gable and rest on the trusses. Then when its time to set out, just run one over at a time. Have did this many times with smaller trusses.
The opening for the garage door is is 4.5m wide x 4m high. But even if it wasnt 4m high, they can be brought in on their sides.