I thought owners had access to all common areas of a site, including the roof as need be, when having a reasonable reason to access them, with or without committee permission?
Not really. For instance, your scheme might not want all owners to have access to your electrical power board or communications room, at their own behest. However, there should be a good reason for refusing a reasonable request for access. Ask the committee again and request a reason for refusal in writing (should it be refused).