Hi
I have written (free) online stair and roof calculators you may find useful.
They draw a plan of the stairs and roof, so you can see the layout

Stairs
http://www.blocklayer.com/Stairs/StairsEng.aspx
Roof
http://www.blocklayer.com/Roof/RoofEng.aspx

There is also a dovetail template generator here
http://www.blocklayer.com/Woodjoints/DovetailEng.aspx
Enter the dimensions of the wood, and tail setout and it draws the template, ready to print, fold over end of wood and cut through