Roberts comes to Seattle from the University of Oregon, where he spent the 2014 season on the Ducks' pitching coach.
At Oregon, Roberts helped the Ducks to a 56-9-1 overall record, a 20-3-1 Pac-12 mark and the conference title.
"I'm very excited to add Mike Roberts to our coaching staff," Tarr said. "He has proven he can develop pitchers of multiple styles. The players he's worked with continue to get better. He's very easy to get along with, and our players will enjoy the natural way he connects.
"From an offensive preparation standpoint, he possesses the ability to mimic whatever opposing pitcher we will face," Tarr continued. "This is a very uncommon thing to have on a coaching staff in our sport. Hiring Coach Roberts is a big piece to our program's continued evolution."
Under Roberts' leadership, the Ducks led the Pac-12 with a 1.82 earned run average while Oregon pitchers held the Nos. 2 and 3 spots in the individual rankings for ERA. Under his tutelage, Oregon's Cheridan Hawkins was named Pac-12 Pitcher of the Year in 2014.
Prior to joining the staff at Oregon, Roberts spent three seasons coaching the pitchers and catchers at the University of Wisconsin-Green Bay.
Roberts, an accomplished pitcher in his own right, won two ASA national titles, an ISF Junior World Title, eight New Zealand national championships, an NAFA Triple-A North American crown and an Australian state title as a pitcher.
A native of Auckland, New Zealand, He pitched in 13 ISC world club tournaments and was a member of the ISF Samoan men's national team. Roberts twice earned ASA and NAFA All-America honors and won numerous U.S. and New Zealand MVP awards. He also earned the New Zealand Herald Junior Sports Award, given to the top five prospects in all sports in his home country.
Roberts began his coaching career as head coach at Denmark (Wisc.) High School, where he posted a 51-19 record in three seasons. He was also a private softball pitching instructor before and during his time as a high school coach.
Roberts and his wife, Therese, have two children, Lauren and Mitchell.