You can use the Move Whole Element tool to move a dormer roof to another spot on your roof.
To move a dormer roof:
Click on the edge of the dormer roof to select it.
Right-click and select Move Whole Element, or select Edit > Modify Element > Move Whole Element.
Click anywhere on the screen, then drag to move the dormer roof.
When the dormer roof is where you want it, release your mouse button.
Note: If the dormer has walls, you need to move the walls separately. To move the dormer walls, click on one wall, Shift+click to select the remaining walls, right-click and select Move, then click and drag the walls into place.