The Japan international, signed from Bologna on deadline day, can play at centre-back or right-back.
He lined up at right-back for his debut against Norwich City last weekend, which the Gunners won 1-0.
Asked where he sees his best position during his first interview with the club, Tomiyasu replied: "For me it doesn't matter because the most important thing is to play in the game.
"So if the coach told me like, "You have to play striker" then I'll play striker. So, yeah, for me it doesn't matter which position I play."
On what Arsenal fans can expect from him, he added: "I can play with both feet, I can play every position as a defender. And I'm an intelligent player so I can always read the next situation."