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"
"to await the stars"
"calm, healer"
"from the new estate"
"dwelling, honor"
"land, territory"
"supplanter, held by the heel (via Jake/Jacob)"
"new house, new home"
"of the Jordan River"
"son of the renowned ruler"
"royal dynastic heir (constructed language)"
"resolute protector, determined guardian"
"legendary divine smith (from Völundr)"
"sun, throne"
"beloved, dear one"
"little king, kingly"
"son of the gray-haired one"
"Noble ruler; wise and powerful leader. A variant of the Old German ..."
"son of Alexander (defender of men)"
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.