Learn Russian: Это был человек невысокого роста и скверного характера. - It was a person of short stature and nasty character.

This sentence uses the Genitive of qualitative description. In Russian, permanent, inherent characteristics like height (рост) or personality (характер) are described by putting the noun and its modifying adjective in the genitive case right after the person or object being described. You would use с plus the instrumental case for accessories, temporary states, or distinct physical additions (e.g., человек с усами - a man with a mustache).

Could I say короткого роста instead of невысокого роста to mean 'short stature'?

No, this is a common trap! In Russian, короткий means 'short' only in terms of physical length of objects (like a short rope) or time (a short meeting). To describe someone's height, you must use невысокий (not tall) or низкий (low).

Why use this genitive structure instead of just saying Это был невысокий человек?

You can absolutely say невысокий человек! However, using the genitive of description (человек невысокого роста) is a stylistic choice that sounds more literary and descriptive, much like 'a man of short stature' compared to 'a short man' in English. For характер, this structure is incredibly useful because simply saying скверный человек would mean 'a vile person' overall, rather than specifically pointing out their nasty temperament.

Why is the nominative case (человек) used after был here, instead of the instrumental case ()?