Chances are, it's High Evolutionary, aka Herbert Edgar Wyndham
Evidence is not 100% conclusive but plausible:
The planet that GotG land on after escape from Sovereign fleet and where they meet Ego is called Berhert
That's an anagram of "Herbert" which is High Evolutionary's first name.
Credit: Second Son channel on YouTube
Now, as per the question, Gunn explicitly stated that Rocket's creator was Easter-Egg-hidden in GotG#2 film; and this is the only known possible clue.
Although High Evolutionary had nothing to do with creation of Rocket in the Marvel comics, he is generally very suited to the role:
Although expelled from the university for his single-mindedness, he finally succeeded in evolving his pet Dalmatian Dempsey into a humanoid life form with the intelligence of a chimpanzee.
The two characters did intersect in Marvel comics:
The High Evolutionary appears in the Guardians of the Galaxy animated series, voiced by Nolan North. In the episode "Evolution Rock", he and his insectoid creations have captured Rocket Raccoon, Groot and Captain Marvel to experiment on...
Last, but not least, Twitter account "Rodger Wardell" confirmed this when discussing Guardians of the Galaxy Vol. 3:
Roger Wardell @RogerWardell
Rocket's creator is the High Evolutionary, Drax is in for a big surprise when he discovers his daughter is alive. Rocket also gets a love interest in the form of Lylla. Nebula and Star Lord will grow into closer friends.
3,250 8:34 PM - May 7, 2019This isn't an official MCU account, but as per comicbook.com,
it previously had a string of Avengers: Endgame leaks last December that all ended up correct in some shape, way, or form.
