おめえ which is a broken version of おまえ means “you“ in a very rough and aggressive way.
も means “also”.
ボス means “a boss“.
なった is the past tense of なる meaning “to become” which follows a noun with the particle に.
んだろ in a question means “right?” used in male speech when asking for confirmation from the listener.
この means “this” as an adjective so it’s always followed by a noun. And the noun is 瓦礫の山: 瓦礫 means “rubble”, the の particle is used to explain what the following noun is made of and the following noun is 山 which literally means “a mountain” but it’s also used to mean “a pile“.
で is the particle to indicate the location where the action has taken place.
よ is the particle used in male speech to make the tone stronger which often sounds rough and aggressive and it can be used multiple times in the middle of a sentence. In this sentence, the word order is inverted for emphasis, so this よ is actually in the middle of the sentence as この瓦礫の山でよ、おめえもボスになったんだろ？