I know I'm pretty far along this tree not to know this by now, but: how can you tell when it's translated as an object, "red roof," vs. when it's translated as a descriptive sentence "the roof is red"? Is there a dative thing going on here that I'm not seeing, or something else maybe?
It is word order. When acting as a modifier (ex. red rood), adjectives will always without exception precede the noun they modify. If it comes after, it will always be a sentence.