I agree with Robert, avoid re mapping unless necessary. Create the login with the correct SID, this script is also useful for generating CREATE LOGIN ... statements from a source server. The roles should be pretty easy for you to figure out 😉

SELECT'CREATE LOGIN ' + name + ' WITH PASSWORD = ' +

sys.fn_varbintohexstr(password_hash) +

' HASHED, SID = ' + sys.fn_varbintohexstr(sid) +

', DEFAULT_DATABASE = ' + QUOTENAME(default_database_name) +

', DEFAULT_LANGUAGE = ' + default_language_name +

', CHECK_EXPIRATION = ' +

CASE

WHEN is_expiration_checked = 0 THEN 'off'

ELSE 'on'

END +

', CHECK_POLICY = ' +

CASE

WHEN is_policy_checked = 0 THEN 'off'

ELSE 'on'

END

FROM master.sys.sql_logins