When installing Active Roles server and specifying the SQL server and/or previous configuration DB the following error may be returned during the instalaltion process:
SQL Network Interfaces: Error Locating Server/Instance Specified [xFFFFFFFF].
This can be resolved by making sure that the Active Roles Server service account and the SQL server service account are running with the same credentials.
If this does not resolve this issue then something else is the cause of the problem and SQL configuration needs to be analyzed further. Check if relevant ports are correctly opened and if SQL is correctly configured.