In reply to Gaijin:
Congrats on the permission.
You are adding significant additional live loading to the structure as well as the dead loading of the timber climbing structure itself. I'm a structural engineer and specialise in timber climbing structures. If you email me the following details about your existing roof structure I can check their suitability.
-Rafter width and depth
-Rafters spacings measured from center to center
-Greatest Length of rafter from attic floor to ridge/purlin
-Angle of roof
(Or instead of the latter two the greatest horizontal distance from wall to ridge.)
-Existing roof covering. Type of tiles etc