What we are looking for:
Insulation amount, installation  method
Ventilation – checking for blockages or damage
Fire Separation – fire resistant walls
uninvited animals – checking that any points of entry and ventilation points are not blocked

Reasons why inspector may not be able to safely enter roof space:
– Fragile or damaged ceiling joists or roof trusses may be unable to support the inspector
– Roof framing is obstructed by insulation making traversing the roof space unsafe because of low visibility for safe foot placement  
– Roof space is inadequate as a result of low pitch roof design
– Electrical hazards