Hello Wombleflow Have dealt with this scenario on numerous occasions in the past. Firstly I do see were your boss is coming from as Mobile Cranes are very expensive to hire even for a day. You do not mention the height of the scaffold / roof height or the size of the trusses etc. However do try to avoid the Manual Handling of these trusses as they can be awkward to handle, particularly passing them up on the outside of the scaffold. What I implemented was the introduction of a Scaffold Loading Bay that was Tied into the Scaffold then used a Telehandler to transport the trusses neither onto the Loading Bay itself if its was big enough or a across the Loading Bay handrails that can be easily handled by operatives. In regards to Scaffold Hoists, I imagine you are suggesting Scaffold Ginny Wheels. Remember their Safe Working Load is kg so this may not be ideal.

Hi, This is not an area I have any first hand knowledge of, its just that I only read this the other day. http://www.hse.gov.uk/pUbns/priced/hsg33.pdf Page 37 - It might be helpful. Cheers Andy