The music that accompanies classic film noirs is definitely sui generis.
Rozsa's noir film scores no doubt evidence the sound as well as his own style and sound, but his non-noir scores will sound different.
You can count on just about any composer who wrote a score for a noir to have the noir sounds in it. Examples include
Hans J. Salter
As with all facets of noir, there is a central tendency ( or maybe two in a bi-modal distribution) for sound, but variation away from the mean to the point where some scores are unique. The central tendency is orchestral. Jazz is notable on a few noirs, but it is not the central tendency, despite the perhaps common or vulgar notion that noir music is jazz. Where jazz is in fact used the whole score will usually be by some well-known jazz composer or artist, and the score won't sound the same as in the much more frequent central tendency which is orchestral. Jazz scores include Elevator to the Gallows, Odds Against Tomorrow, The Strip, The Big Combo theme, the Man with the Golden Arm, and I'd check Private Hell 36. Many movies have some jazz in them or some interludes, but the main score is orchestral.
If I am right that most noir scores are orchestral, the much harder question for those of us who are not familiar with how to describe music (and that includes me) is how to characterize these sounds. It's easier to hear them and recognize them than to say what distinguishes them, at least in my case. Max Steiner opens "Beyond the Forest" with a strong full sound, sometimes pairing brass and violins, it's almost violent, it's passionate. Later he gives us some highly romantic sounds, sometimes using only a piano. Roy Webb opens "Race Street" with music evoking a busy city, as the camera pans over a cityscape.
The noir score typically develops a kind of mystery or emotionally unresolved character in many situations as if it awaits development of some action.
There is tension implicit in noir scores, passion and movement from one sound to another without always following through on a theme or developing it or resolving it right there and then. It's orchestral but not conventionally orchestral.
You will find a typical essay on music having difficulty pinning the thing down. As here: http://filmnoironline.com/music.html
This mentions several tendencies and they contrast sharply. In one spot, it emphasizes the orchestral: "... His [Rozsa's] music was at times Wagnerian, brooding and atmospheric, conveying the dark moods of noir, and at other times frenetic and electrifying, suggesting the fast pace of modern urban existence." Also: "[Deutsch] laid the foundation for a musical language of noir evocative of foreboding, suspense, surprise, high action, or the shock of sudden recognition."
But then it goes on to say "The music of noir is sexy." However, it's referring to songs inserted into the films, not the composed cues and scores.
Therefore, their basic idea and mine is that the scores are mainly orchestral.