Angle of the roof can be measured by using the Roof angle formula given below. Compute the run and roof pitch by substituting the rise and slope value in the respective formula. To fine the angle first divide the rise by the slope value then multiply the result with 100. You need to divide the rise value by the obtained result. Again you have to determine the tangent for the value you have obtained. This would be the angle of the roof pitch. Roof pitch is the amount of rise a roof.