This should be simple but I can't find a solution without reading direct from system tables, which I don't want to do in this case as it's required for application code.

eg... db role name : db_myrole

select system_user -- identifies the user correctly

eg. system user : myDomain\fred

sp_helprolemember db_myrole -- shows db user 'fred' as a member

is_member -- no good as only works for 'current_user' eg. dbo

So, yes, I could use sp_helprolemember, dump out to temp table and query the temp table... but messsy. I really thought there would be function like IS_MEMBER but can't find it.