Are valuation rolls useful for tracing missing persons?

Not really. Valuation rolls for domestic properties have not been compiled since 1989, so are now out of date. Secondly they are usually arranged by street, not by personal name. Electoral rolls are slightly better, because they are updated annually and include the names of more people, although Electoral Rolls, again, are arranged by street name. It is possible to buy databases of voters rolls, produced commercially. For further advice on tracing someone you have lost track of read Colin D Rodgers, Tracing Missing Persons: an introduction to agencies, methods and sources in England and Wales (Manchester University Press, 1986).