You really think the Flute Concerto is Rouse's best work, kyjo? In my opinion, it's one of the middle of the road (leaning toward the bottom end) works of Rouse. Yes, the odd numbered movements show off his gift for heartfelt melodic invention, but the quicker sections totally lack the momentum you hear in his more characteristic quicker works. The more melodic movements don't really leave me feeling sympathetic to his aims in the work, either. The Symphony No. 2 from that Teldec disk is a real masterpiece, however. The middle movement is the antithesis of the Flute Concerto's Elegy. It shows his feelings toward Stephen Albert's death, a composer that was a great friend of his. It comes as a shocking event that changes the rest of the symphony. You can almost feel Rouse's anger and anguish at losing his friend.
I'll take a stab and say what three pieces of his I would choose as his greatest successes: Symphony No. 1, Trombone Concerto, and Phantasmata.
Phantasmata is the earliest work here, and it is perhaps the most successful of Rouse's less serious works. The first movement serves as a sort of quiet, atmospheric, otherworldly prelude to the other two movements, which are able to be performed alone. The second movement, The Infernal Machine, is a cheeky perpetuum mobile that shows off lots of rhythmic and textural invention. The last movement, Bump, was described by Rouse as a sort of "conga line in hell" because of the ever-present bass drum hit on beat 4.
The Symphony No. 1 is a one movement symphony that definitely shows off Rouse's love for the famous symphonists, and for his love of those composers that wrote great adagios, such Shostakovich, Sibelius, Hartmann, Pettersson, and Schuman (he cites them in his program notes). One can even hear a choir of Wagner tubas in certain parts of the work, as one would hear with Bruckner. There's also a fugato on the DSCH theme near the beginning. Toward the climax of the work (the biggest one, for there are a few), he even uses a Mahler hammer to punctuate it. There are some great chorale-like passages that show off some interesting harmonies and his gift for melody. However, it's a tragic work through and through, and it ends without a shred of optimism.
The Trombone Concerto is the work that won him his Pulitzer, and it was written in memory of Leonard Bernstein. There is a definite air of sadness in the outer movements, and he even quotes part of the Kaddish Symphony in the third movement. The very fast second movement is stereotypical Rouse, with percussion and lots of loud orchestral interjections. The trombone part is very acrobatic and virtuosic here, and the movement ends with 4 hammer blows. The third movement brings back some melodic material from the second movement, only slower and more passionate, and it closes the concerto much like how it began.