This is done under the web console. Click on Admin - Account Manager - select the account you want to disable IPAM for. On the bottom of the page is IP Address Manager Settings, expand this. You can then change the IPAM Summary View to None. This will remove the menu item of IP Address Manger.
Hope this helps.
Doh! Somehow my brain missed this - I guess I was too busy trying to figure out why it wasn't under Roles.