Regarding the IOS,

[Dootguy_SeventyForty]

Now, do you have to hit the Romero Head with the rocket? Or is the BFG an option?

[Edward850]

Has to be a rocket. Hitting the IOS is dependent on splash damage as direct line of sight isn't possible. The BFG isn't an explosion, so if the BFG worked literally any weapon would.

Edited March 10, 2019 by Edward850

[Dootguy_SeventyForty]

Interesting, thanks!

[Empyre]

That is assuming that you mean specifically in Doom II MAP30.  If it is a custom map, line of sight might be possible.  Also, if you noclip to it, any weapon will damage it, even your fists.

Edited March 13, 2019 by Empyre
embarrasing spelling error