SELECT round FROM table_24853015_1 WHERE class_d_winner = "Roy Salvadori" AND class_b_winner = "Alan Hutcheson"
Di babak manakah Roy Salvadori memenangkan Kelas D dan Alan Hutcheson memenangkan Kelas B?
CREATE TABLE table_24853015_1 (round VARCHAR, class_d_winner VARCHAR, class_b_winner VARCHAR)