Every county, district, unitary and metropolitan council is required to appoint an officer of the council to be the RO for the election of councillors to their local authority.1
London Assembly constituencies are made up of two to four London boroughs. Typically, the Returning Officer of the largest borough (usually the one with the most registered electors) is the Constituency Returning Officer (CRO). The CRO is designated by an Order made by the Secretary of State.2
If you are not designated to be the CRO, by virtue of being the local government RO, you will be a Borough Returning Officer (BRO) for the GLA election. You should ensure that you have appropriate insurance cover. You should be prepared to demonstrate robust planning and decision-making processes in the event of any challenge to the elections and a claim against this cover.
The team at your council dealing with insurance may be able to help determine what existing cover is in place and available, and to provide advice as to whether it should be extended.