回し者 (mawashi mono) originally means “a spy”, but nowadays it’s more often used to indicate a person who advertises something (often in a stealthy way).
It is usually used as 回し者ではない/ありません, meaning “I am not a 回し者” or “回し者みたいだけど…” meaning “I may sound like a 回し者, but…” when you want to clarify that you are not a shill or salesman hired to advertise some services/products. For instance, people often say this phrase before or after they enthusiastically recommend them to others.
アップルの回し者みたいだけど、今年の新しいiPhone と Apple Watchめっちゃおすすめ。
I may sound like a salesman of Apple, but I really recommend the new iPhone and Apple Watch this year.
* めっちゃ: a casual way of saying とても
ステマ: short for ステルスマーケティング (stealth marketing)
~とは無関係 (むかんけい) の人 (ひと): a person who is not related to ~
Meaning of ふつつか者 (futsutsuka mono)