As mentioned in the 訳（わけ）だ grammar point, わけ is a 名詞（めいし） (noun) that is used for strong determination/conclusion in Japanese, in the same way that ‘so’ is in English. Naturally, this determination may sometimes be negative, as is the case with わけではない. ではない being the conjugated form of the 助動詞（じょどうし） (auxiliary verb) だ, the 副助詞（ふくじょし） (adverbial particle) は, and the い-Adjective ない.
わけではない may be translated as ‘it doesn’t mean that (A)’, or ‘it’s not the case that (A)’. Although, ‘it is not necessarily so that it’s (A)’, or ‘so it’s not (A)’ are closer to the actual nuance of わけ. わけではない can be used at the end of any sentence, so long as the word before わけ is in 連体形（れんたいけい） (attributive form).

• 日本（にほん）に住（す）んでいるから日本語（にほんご）を話（はな）せるわけではないです。私（わたし）は日本（にほん）に来（く）る前（まえ）に日本語（にほんご）の勉強（べんきょう）をしていました。
  It is not the case that I am able to speak Japanese because I live in Japan. I studied Japanese before I came.
• 私（わたし）の家（いえ）は広（ひろ）いわけではないけど、小（ちい）さくもない。
  It is not necessarily so that my house is big, but it is not small either.
• 仕事（しごと）が大変（たいへん）なわけではない。忙（いそが）しいだけ。
  It's not that my job is difficult, it's just busy.
• 熱（ねつ）のわけではないけど、体（からだ）がだるい。
  It's not necessarily so that I have a fever, but my body feels heavy.

As always, では may be replaced by じゃ.

• あの監督（かんとく）は有名（ゆうめい）だけど、映画（えいが）を監督（かんとく）して有名（ゆうめい）になったわけじゃない。
  That director is famous, but he did not become popular because he directed a movie.
• あなたが悪（わる）かったって言（い）っているわけじゃない。
  It's not so that I am saying that you were in the wrong. (I am not strictly saying that you were in the wrong)