I use similar tackle to this link
_http://www.applegroup.uk.com/shop.htm
2 rope system.
Basic description
Main ladder fastened to the wall via eye bolt and ratchet strap(ladder mate at bottom to foot ladder with non slip mat/leveller), rope is fastened around top rungs and microlite, which then runs down to the base of the ladder where it is attached to keep it tight.
Now using rope grab and harness ladder access is now safe.
If roof access is required,
2nd rope hooked onto the top of the roof ladder, both ladders then ratcheted together nr guttering.
Cows tail(Hook) allows me to hook onto ladders, giving extra point of contact, useful when moving between ladders or transfer of rope grap between 2 ropes.
Using harness ladders can be scaled safetly and once you get into swing doesnt slow you down too much.
If i need to leave the roof ladder-i use the chimney strop(fastnen around chimney connect my harness too it
Hope that helps