Roof Pitch is simple the number of inches the roof drops vertically per foot.
Sooooo, put on your Trigomometry Hat and 'veiw' the roof as 2 Right-Triangles 'attached' at the vertical. Simply draw a picture of the house's roof on a piece of paper, and where the 2 eaves (or edges) of the roof are, 'connect' them with a horizontal line. Then, where the 2 roof lines meet (at the peak), draw a line vertically DOWN to meet the horizontal line you just drew. What you have are 2 Right Triangles 'connected' at the vertical.
Now, 'toss' one of the triangles away. (Redraw just one of the triangles if you must.) Do you remember that A-squared + B-squared = C-squared??? Side C is the hypotenuse (or the 'sloping' side of the 1 remaining triangle.) Go back to your roof and measure mentally figure out where your Right Angle is going to be. (The Right Angle is the location where the vertical and horizontal 'sides' of your roof-triangle meet! From there, you can measure the Rise and the Run (ie., the Vertical and the Horizontal), and then figure out (if you must) how 'long' your roof will slope. At the same time, you'll have already answered your question as to the 'height' of the roof.
Don't forget - To figure out the length of any triangle, you must take A-squared + B-squared to get C-squared. For example, label one side 3' and label the other side 4'. Square them up (3x3 + 4x4 = 25), and take the square root of 25 to get 5. Hence, 3-squared + 4-squared = 5-squared, right? Enjoy! (Math is something I studied in college for 2 years and then realized they made computers to do a lot of the computations ...)