Hi @rpsimon ...
Full disclosure, I'm not exactly sure if this is what your SIS developer is asking for, but I'll attempt to help answer. Assuming that you are a Canvas administrator, I think you'd first want to go to your "Permissions" tab (How do I manage the Permissions page?) and then look at your "Account Roles" tab:
If there is not an existing role (column) that meets all the permission requirements for the specific role you want, you may want to consider creating a new role and then set the permissions specific to this new role. (Or, maybe you have an existing role that you could enable some additional permissions?) There are three rows related to SIS: "SIS Data - Import", "SIS Data - manage", and "SIS Data - read". There may be other permissions you'll have to enable for this role, too, but I'll let you decide which to enable and which to keep turned off.
Once you have the permissions configured the way you want, you can then go to your administrative "Settings" page in Canvas, and then click on the "Admins" tab. Here is where you can add an individual with that role/permission. How do I add an admin to an account? (You can also add people at the sub-account level using this same Guide.)
Again, this is a lot of speculation on my part, and I'm not sure you'll need to do all of this. But, hopefully this will help in some way.