Hi Larz,
Yes it can be done but by default TFP does not have the purlins. If you want them visible, as in the photo you would have to add them individually.
You can use the straight line tool on the Layout toolbar to simply make a 2D line, right click it and choose "Convert to Member" (all sorts of shapes and sizes to choose from) then you can elevate it and right click 'Adjust to Plane' or something like that - can't remember exactly the words at the moment but it will snap it to the slope. Before you do duplicate it the number of times you necessary.
Or ...
In a new blank project, you could duplicate the members (on the ground the right distance apart), turn off the Terrain and export them as a 3DS and import again into your model. This way you would have a set of purlins. You can adjust the angle to the same as the roof after import and elevate them into place. As long as they are all the same length (as in the photo) this would probably be quicker. You can extend the length if necessary after import.
If you need more explanation of those options just ask again.
Allan