Now I am talking mainly residential roof's here but I don't discount the commerical roof, with many commercial buildings built using residential practise. You may need to refer to the earlier parts of this series 1, 2 & 3.
The simple Cutout for the roof object is just a matter of tracing the outline of your roof and editing the edges (right click option) of the cut out portion and changing the overhang and the slope to 90. Just remember if you miss a point (vertex), you have to recreate the whole roof!
What about the Cutback eave? I showed this in my wall example, having to edit my external cavity wall to cater for a cut back eave. This happens not infrequently here in West Aus. So how do we wrestle the roof object into cutting back the eave and showing the eave in one straight section. You would assume that you should have two end points and a point (vertices) for where the roof eave changes from overhang to none but you will be wrong. The Roof object can't do it and your eave goes strange. You need to have an extra point and the extra edge has to have 90 degree slope. That's illogical to the roof shape but it works. Once constructed you need to drag your points very close together so that the raking portion of the eave appears at right angles to the roof pitching line for a spandrel to end the eave overhang.
What about different plate heights? Can the Roof Object handle this? Very easily!
Construct your roof at your main height. Select your roof, right click and select 'Edit Edges'.Select the edges you want to raise and enter the new pitching height. You are done.
But remember that the roof object can't overlap itself UPDATE - WRONG so for e.g. the eave can't overlap the lower roof portion. So how can you do that? Resort to slabs? Chicken! Here's a method that takes just a little planning. WHILST this technique works, being able to overhang itself is probably a better option as the valleys will self heal at the right height without you have to input.
Create the main roof and trace around the valley connecting the main roof to the raised portion. These connecting edges will get a 0 overhang and a 90 slope. Now create a second roof to position into the breach and you are done. Your new roof can now overlap the main roof and there are no unwanted lines on your drawing.
Tip: As I've pointed out before, don't worry about getting this cutout right for your design development stage. Just overlap roof objects as required to get your outer shape as you need. Once the design is final you can plan & trace and replace so your sections will look correct too.
Well that's probably as many tricks as I know to using the aecRoof Object without resorting to slabs. UPDATE - LOL Hopefully I've helped you to be able to use it more extensively, at least in the design process and be able to get it to look how you want.
Oh and I have added some more detail for a Dutch Gable and some interesting tips for gable infil and about the behaviour of the aecRoof object as a barge to Part 2 of this series. It's in the centre of the post if you don't want to read it all again.