Rostam sits next to 3 phonetic neighbors — Rustam, Roshan, and Reza are the closest matches by sound. Most share Rostam's Persian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"strong, heroic warrior"
"Gracious, charitable person"
"firm, strong, steadfast"
"young, heir (alternative)"
"heart's dear one"
"little Hasan (diminutive of good)"
"illumination of the prophet"
"uncle, kinsman (alternative etymology)"
"archer (from the myth of Arash Kamangir)"
"treasurer"
"splendid, of radiant birth"
"Canopus star, bright star"
"azure, enamel, gemstone"
"birth, nativity"
"honorable (title of respect)"
Similar sound: These names share phonetic patterns with Rostam — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Persian/Avestan origins, giving them the same cultural heritage as Rostam.
Rhythm: Rostam is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.