The Roblox 'oof' can be sampled here, while the original Messiah implementation can be heard here. Yep, it's the same sound, and the creator of that sound, Intellivision Entertainment CEO Tommy ...

The Roblox oof. A loud, muffled cry of pain whenever your blocky little chap dies. It's an iconic sound, one that is so ingrained in my memory I'm not sure I'll ever forget it.

The Roblox "oof" sound, which became famous not just with players but around the internet as a meme, has been removed from the game entirely due to a licensing issue.