When and for what role did the youngest player appear in his first match?
When refers to Match_Date; youngest player refers to max(DOB); first match refers to min(Match_Date)
SELECT T1.Match_Date, T4.Role_Desc FROM `Match` AS T1 INNER JOIN Player_Match AS T2 ON T1.Match_Id = T2.Match_Id INNER JOIN Player AS T3 ON T2.Player_Id = T3.Player_Id INNER JOIN Rolee AS T4 ON T2.Role_Id = T4.Role_Id ORDER BY T3.DOB DESC LIMIT 1