It is apparent that you have not actually stepped through all the parts of my description at my first image, which clearly tell you what to do.  See in particular the boldface entries, one of which deals specifically with the straight-to-sloped step [that's why they're in boldface -- to be sure you notice].

Try and use them or eventually use the ALIGN command.

I'm not really interested in tile roofs but this PDF is very well made for a person that wants to get deeply in the subject, which I'm not, sorry.

I really think the description at my first image tells you what to do -- again, go one sentence at a time.  One suggestion that may help is that you draw the white Circle centered at point A, and then Move it down the slope.  It looks like maybe you are unsure about moving or copying something at a given distance in a given direction.  If you don't know how to do that, you're not ready to model a house in 3D with individual roof tiles, so get some basic understanding of the program first.

I'm curious as to whether anyone actually makes a roof tile that's 1 unit x 10 units in cross-section.  If so, I wonder about their details of installation.

That will be up to the tile manufacturer.  Look at their standards, which should specify exposures as well as minimum roof pitches.

John wiley & sons, best practices guide to residential construction

Or search directly the document :

0471648361.excerpt.pdf