サッカー means “soccer”. Sports in Japanese are mostly named using katakana as many of them are imported from other countries. For example, テニス (tennis), ゴルフ (golf), バレーボール (volleyball), バスケットボール (basketball), ラグビー (rugby), バドミントン (badminton) and so on. On the other hand, Sports of Japanese origin are named using Kanji such as 空手 (karate), 柔道 (judo), 剣道 (kendo), 弓道 (kyudo), 合気道 (aikido), 相撲 (sumo) and so on. There are also sports which are imported from other countries but the name in kanji has become more common such as 野球 (baseball) and 卓球 (table tennis).
やろう is the volitional form of やる meaning “to do”. So サッカーやろう means “let’s play soccer”. You can also say サッカーしよう which is the volitional form of する but やろう sounds more rough and casual. The direct object particle を is omitted which often happens in casual speech.
ぜ is the sentence ending particle used towards equals or inferiors in male speech. It’s used when you want to emphasise or make sure of something in a friendly way, or when you simply want to sound cool and manly. When it’s used with a verb volitional form, it sounds more encouraging. Although, you rarely hear it in real conversations as it sounds a bit too rough or too masculine.