The slanted ceiling in this photo is simply the natural result of using the space in what would otherwise be unfinished attic as living space.

Any home with a roof pitch of 8:12 or better has a pretty good volume of space above the first floor in what might otherwise be the attic (I've been in a number of attics lately that I could fit my entire house inside, they were so big!).

In the room pictured above, this space under the roof has a flat gable end in the center of the photo and what appears to be a shed dormer to the right (and to the left out of the photo), creating more ceiling height and allowing that bank of windows. A structure like this will generally have to be "stick-framed", that is, built from individual large framing members as opposed to "truss-framed", built from engineered assemblies of smaller framing members.