The oof sound comes from Messiah (2002) and was licensed to Roblox; anyone using it in their Roblox experiences would have to pay one dollar (or 100 Robux.)
Tommy Tallarico is the composer of the oof sound; Tallarico is a game composer and, more recently, the CEO of Intellivision.
Kotaku provided some additional context on the copyright issues that led to the sound effect being pulled.
For those who miss its predecessor, the ‘oof’ sound will likely live on in TikToks and YouTube videos, as part of the memetic quilt of the Internet.