Here is a query I dug up from sp_helprolemember to show a list of database role members.  I cleaned it up to use INNER JOINs instead of commas/old style joins.

SELECT  DbRole = g.name,
 MemberName = u.name
FROM  sysmembers m
INNER JOIN sysusers g ON
 g.uid = m.groupuid
INNER JOIN sysusers u ON
 u.uid = m.memberuid
WHERE g.issqlrole = 1
ORDER BY DbRole