The faces that generate roof dormers...

1. ...have to be rectangular quads (all corners 90°)
2. ...need to have 2 parallel edges that are perfectly horizontal

If your roof shape is different you can use edge cuts or loops to create rectangular areas within them.

To activate dormers, select the "DORMER?" attribute in the Mesh Data Panel under Attributes. Also select the relevant faces. Then go to Mesh-> Set Attributes and click on the checkbox:

Roof generator is not optimized for inside shots. Planks and rafters were only added because you can occasionally see parts of them from an outside perspective. There is no modeled room behind the window that is presentable. 

Materials are applied in the modifier tab. The materials that you have in the Material property tab get overwritten. Every material needs to be prepared with a custom "Attribute" node that replaces the "Texture Coordinates" node. The procedurally generated UVs can be accessed this way.

You have to enable Ambient Occlusion in your scene. You can set its strength to something close to 0, if you don't like the look, but the option has to be turned on. The shader uses AO to control roughness and dirt, feeding the system with its own independent values for distance and strength.  

Yes you can. First of all you need to prepare your tile geometry. Make sure that it is facing upwards (Z-Up) and you applied all transformations (Object->Apply). Make sure it is NOT solidified, the modifier will take care of that. Check the geometry of the tiles that are already included in the file for comparison. And you should probably create a new unique copy of the modifier to not overwrite existing profiles.
In the node editor you then have to edit the parameters on the roof tiles subgroup. Other subgroups allow similar individualization for ridge or inside part of the roof.