I really can't remember everything from the 1986 movie or G1 S3, but... I don't really remember Rodimus talking much about his life prior to becoming the Prime. If we're taking lore SOLELY from the show and movie, given how often G1 just had the Autobots or Decepticons just Build New Guys, I don't think it's too unreasonable for some casual (or forgetful, idk) fan to assume that Hot Rod was built on Earth in the time skip period between S2 and the movie. You could totally do an AU interpretation where Rodimus and Daniel are the same age or close to it.

Some Autobot back on Cybertron: "When was this new Prime constructed? I don't recall meeting him before."

Rodimus: "I'm ten."

Some Autobot: "Ten what? Ten million? You wear your years extremely well, then. You can't possibly be only ten thousand, that's much too young for a Prime-"

Rodimus: "Just ten years old, buddy."

Some Autobot: "..."

Rodimus: "And trust me, every single one of them has sucked ass enough for a million. Are we doing these super important galactic politics today or what?"

Some Autobot: "I have energon stones in my filtration tanks that are older than you."

Rodimus: "Yeah, and I have to go beat the shit out of some Quintessons with my bare hands later, AND I still need to squeeze my daily crisis of depression, guilt, and self-loathing in somewhere because Ultra Magnus says I'm not allowed to put it on the official schedule anymore. Are we having this meeting or not? I'm a busy guy."