Half the time, and I really do mean half, the object file that Roblox generates can’t actually be imported into Blender. Obj exports directly from studio are in fact a dice roll. I’ve actually stopped using Roblox meshes for this exact reason.
A game engine developed by a multi billion dollar company that can’t even export one of the most essential file types for external modeling programs, because they can’t fathom how this would benefit game development in any way.