Tyrer, 27, was coached by new Roughyeds boss Scott Naylor during his academy days at Salford, and has also played for Swinton in the Championships.
He said: “I was looking for another club and as soon as I heard Scott was the new boss at Oldham I gave him a call.
“He’s a good coach and I know what he expects of his players. He’ll have his sights on honours, no doubt about that.”
Naylor said: “I know him well from our Salford days. He won’t take a backward step, and you need that in a front-rower.
“He’s versatile, with good skills and with an engine that enables him to play for long spells.”
Tyrer’s signing takes Naylor’s squad numbers up to eight for the new season.