To determine the height of the roof at its highest point, we can use trigonometry. In this case, we can use the sine function to find the height.

The formula for calculating the height of the roof is:
Height = Width * sin(Angle)

Given:
Width = 70 feet
Angle = 35 degrees

Using the formula, we can calculate the height as follows:
Height = 70 * sin(35)
Height 40.35 feet

Therefore, the roof needs to be approximately 40.35 feet tall at its highest point for it to have an angle of 35 degrees.