1) draw line at pitch of roof
2) extrude line to length of roof
3) convert to editable poly
4) select edges
5) connect edges (number of tile division)
6) extrude (height of roof tile)
7) champer (to profile desired)
8) select first edge of oppisite side of roof
9) connect edges (number of tiles)
10) champer edges (click open option)
11) select elements and rotate
12) scale to overlap
13) add shell modifier

Video presentation by: Rod Thonen