I have used disposable roof anchors with wire rope loops attached similar to this,
http://www.guardianfall.com/anchor_snappy.cfm The anchor is nailed or screwed to framing either ridge or rafters and remains through the construction and becomes part of the building. Decking and panels can be applied over the brackets, the wire rope loop must be long enough to come through the surface of the panels. Use a carbiner to attach lifeline to bracket or loop.
This type anchor bracket is for a single a lifeline and worker but it is inexpensive, $4 to $5 each, and multiple hitch points can be placed along the roof.
