Join to only the "latest" record with t-sql

select a.*, bm.MaxRowDate
from (
    select TableAID, max(RowDate) as MaxRowDate
    from TableB
    group by TableAID
) bm
inner join TableA a on bm.TableAID = a.ID

If you need more columns from TableB, do this:

select a.*, b.* --use explicit columns rather than * here
from (
    select TableAID, max(RowDate) as MaxRowDate
    from TableB
    group by TableAID
) bm
inner join TableB b on bm.TableAID = b.TableAID
    and bm.MaxRowDate = b.RowDate
inner join TableA a on bm.TableAID = a.ID

SELECT *
FROM tableA A
OUTER APPLY (SELECT TOP 1 * 
             FROM tableB B
             WHERE A.ID = B.TableAID
             ORDER BY B.RowDate DESC) as B