Monster level determines item level in normal. I am 99% certain that all monsters in throne room are above level 25, which is the requirement for 4 sockets. You must know the monster it dropped from in order to be 100% certain. Or check the level every type of monster that can spawn in throne room. But i am 99% certain all of them are between level 25-40.
https://diablo2.diablowiki.net/Socketshttp://classic.battle.net/diablo2exp/monsters/act5-bloodlord.shtml