Rosco sits next to 5 phonetic neighbors — Roscoe, Rocco, and Cosmo are the closest matches by sound. Most share Rosco's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"roe deer wood"
"noble desire"
"strong-willed warrior"
"modern American creative formation"
"light, splendor, radiance"
"new house of God"
"drawn out of the water"
"security token"
"Western cowboy hat, frontier spirit"
"noble friend"
"calf, heifer (symbolic gentleness)"
"symbol of wisdom and knowledge"
"from the ash tree grove"
"summoner, one who calls forth"
"young, heir (alternative)"
"from the new estate"
"of Tyre, the ancient city"
"Noble ruler; wise and powerful leader. A variant of the Old German ..."
Similar sound: These names share phonetic patterns with Rosco — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Norse origins, giving them the same cultural heritage as Rosco.
Rhythm: Rosco is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.