If you mean you want one end of the pivot line higher than the other (which isn't really possible) then you will need to look at modelling the single roof plane in the 3D window.
You choose the 3 points you want the roof plane to pass through and then define the overall shape of the roof - either a rectangle or irregular polygon.
Then adjust the shape of the roof in plan (or 3D) if necessary.
The pivot line will be placed to the true slope of the roof which probably won't match any of your walls.
Barry.
One of the forum moderators.
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