Something I just discovered is that @Embedded​ fields in Room entities can themselves contain @Embedded fields. For example:

data class Post(
    @Embedded
    val media: Media
)

data class Media(
    @Embedded
    val metadata: Metadata
)

data class Metadata(
    val resolution: String
)

works as you would expect, with resolution being pulled up to the Post entity table. Not sure how deeply @Embedded you can go, or if there are any performance consequences to this, but a neat trick!