I assume that the Buildings insurance cover includes Storm Damage, and the claim that the insurers have approved was made under this section, not for a leaking water tank or burst pipe. The insurance assessor should have checked to ascertain where the water originated, and noted the damage to the roof.
If the insurance covers storm damage, go back to the insurers claims handlers and insist that the roof repairs are included within the original claim.
Dependant upon the height above ground, some roofers will work off ladders, obviating the need for scaffolding - I had some of my ridge tiles replaced/reset by a roofer using ladders (his choice) after a storm had dislodged them, although the assessor had included an estimate of the cost of scaffolding in his offer recommendation to the insurers. I think that there were so many claims after that storm, the insurers were quickly paying out at the lowest offer they thought would be acceptable, without requiring estimates.