Early 20th-century French symphonist Albert Roussel’s charming incidental music to an equally obscure fin de siècle symbolist drama sets the stage for two works highlighting the clarinet’s expressive breadth and sonic depth: Rossini’s irrepressible virtuoso showpiece and American composer David Froom’s winsome, introspective “night songs,” selected for top prize from over 100 entries in Riverside Symphony’s 2019 National Composer Competition. Haydn’s timeless masterpiece concludes the evening in high spirits.