The 29-year-old ended a nine-and-a-half year at Celtic in the summer following the expiration of his contract and has signed a one-year contract at The Hawthorns.
Rogic’s contract also includes the option to trigger a 12-month extension until the end of the 2023-24 season as he prepares to test himself in the English game for the first time.
With Rogic aiming to keep his skills ticking over ahead of the 2022 World Cup – Australia join France, Denmark and Tunisia in Group D – the midfielder will spend the next year in the Championship.
“I heard about the club’s interest in me about a week ago and things moved pretty quickly to be honest. I spoke with the manager and I spoke with my agent and here we are,” Rogic told wba.co.uk.
“It was a pretty broad chat with the manager. He seems like a really good guy and we had some really good discussions. He told me lots about the club, the team and what football is like here.
“Since I heard about Albion’s interest in me I’ve tried to watch as much of them as possible and I’ve been doing my research. I think it’s fair to say the team hasn’t got the results the performances have warranted.
“I know that the manager and the boys are looking to change that as quickly as possible. I’d been set in one place for quite a while and I was looking for a new challenge and a change of scenery and I certainly have that here, so I’m really looking forward to getting started.”
Manager Steve Bruce added: “Tom is a quality player who has played nearly 300 games for Celtic, including a significant number of games just last season.
“He has proven to be a quality player, a serial winner, and a top professional. He can play in several positions across midfield and I’m confident he will prove to be a great acquisition for the club. I’m delighted to have him with us.”
Rogic totalled 46 goals and 49 assists in 272 appearances for Celtic across all competitions between 2013 and 2022 after joining for £432,000 from Central Coast Mariners.
During his time at Celtic, Rogic won seven Scottish Premiership titles, five Scottish Cups and five Scottish League Cups, as well as participating in regular Europa League and Champions League action.
The Australia international was loaned back to his homeland with Melbourne during the second half of the 2013-14 season and has earned 53 caps for his country, scoring nine goals and setting up four more.
Rogic follows the likes of Okay Yokuslu, Jed Wallace, John Swift, Martin Kelly, Brandon Thomas-Asante and Jayson Molumby to The Hawthorns on permanent deals for the 2022-23 campaign.