Afraid it's not that easy. :)
You could say "Rödvinerna är dyra" as well. And for singular, you could say "Det röda vinet är dyrt". It doesn't matter for the eventual semantic meaning, but it's a technical difference, kind of like the difference between "the red wines are expensive" (where red wines is a compound noun), and "the wines, which are red, are expensive".
Edit: Or maybe that actually makes it easier. Who knows? :p
Så det heter "rött vin" eller "rödvin"! When we compose up a noun of adjective and noun we should always use "en" words adjectives... I had thought red wine called "röttvin" :D Btw I'm not native english speaker so excuse my missed up sentences... I'm using swedish course for english speakers to learn both :D