The dome in the picture cost $70-90K, was worth $120K on completion and was up on the market ten years ago at $1/4mn.
If I thought even one ecomodder cared, I could put up a thread on Saving@Home about how to make ceramic hexagonal tiles out of clay and sand and heat.
Edit: I think ice guard is sheet metal above the gutters.
To tear off or not is a judgment call. Ask someone who has looked at it. Roofing squares are 3x3'. Take the rough measurement, adjust for dormers and add 10%.