In the 1990 summer, Riedle moved to S.S. Lazio of Italy for a transfer fee of 13 million DM. During his stint with the Roman the club failed to win any silverware or reach any final, and his best output occurred in the 1991–92 campaign when he scored 13 goals in 29 games for an eventual 10th-place finish in Serie A; for two of his three years, he shared teams with countryman Thomas Doll.