So, how do I measure my roof to determine how many bundles will be
needed?

My house is a conventional rectangular ranch (30'x60') and has a
10'x12' utility room attached on the end of back of house, giving it
an L shape


Need to know the pitch. Then it's simple math and geometry.

... or you can just measure the surface of the roof.

want to try something different, perhaps you could take photos of the
various roof surfaces with both a vertical and horizontal rules in the
photo. Then you can use the photo to figure out the area.

Another way is to use google map satellite view, but you'd need to obtain
the roof pitch some other way