You could try this

;WITH cte AS (

SELECT a.itemid, a.date

, 0 level

, null parentid

, a.itemid rootid, a.date rootdate

, CASE WHEN EXISTS(SELECT 1 FROM @tableB k WHERE a.itemid = k.parentid) THEN 1 ELSE null END hasKiddies

FROM @tableA a

WHERE NOT EXISTS (SELECT 1 FROM @tableB b WHERE a.itemid = b.itemid)

UNION ALL

SELECT b.itemid, ab.date

, level + 1 level

, b.parentid

,a.rootid, a.rootdate

, CASE WHEN EXISTS(SELECT 1 FROM @tableB k WHERE b.itemid = k.parentid) THEN 1 ELSE null END hasKiddies

FROM cte a

INNER JOIN @tableB b ON a.itemid = b.parentid

INNER JOIN @tableA ab ON ab.itemid = b.itemid

WHERE a.hasKiddies = 1

)

SELECT itemid, date

FROM cte

ORDER by rootdate, rootid, level , date

Sorry it's a bit ugly, but it should handle same dates and also multiple levels