Now the 26-year-old is on the verge of being thrown into one of rugby's most daunting challenges when the ACT Brumbies start their season against the Canterbury Crusaders on Saturday.

Scrumhalf Roos has signed a two-month deal with the Brumbies as an injury replacement for Argentina Test star Tomas Cubelli.

The first challenge could be a clash against the Crusaders in a city where the Brumbies haven't won for the past 17 years.

But after enlisting the help of an exercise physiologist, the Sydney-based construction project manager says he's ready to take his shot at the big time.

"It's more exciting than anything," Roos said.

"I've always dreamt of this and always wanted to play Super Rugby, but when that call came I was pretty surprised.

"I always held out hope [of getting a chance]. I recently started training with an exercise physiologist in Sydney and he [Justin Lang] made me believe again.

"He said: 'you've got what it takes' and I'm sitting here now. I feel physically and mentally ready if I get that chance."

Tuggeranong junior Joe Powell will get the first chance in the No. 9 jersey but Roos and teenager Ryan Lonergan are battling for a spot on the bench.

Brumbies coach Stephen Larkham could also opt to go without a back-up scrumhalf for an expected physical battle in Christchurch, but Roos or Lonergan would offer valuable back-up to Powell.

Larkham admitted Roos wasn't even on his recruitment radar until the diminutive Southern Districts player was picked in an Australian Barbarians side to play a pre-season trial against the Brumbies.

"I think he's the right fit for our group," Larkham said.

"Realistically it will take a couple of days for it to sink in. But having seen him train for two days now, he is the right fit.

"It's very tough to pick everything up in two days but he's in contention there. The trial is where I probably first noticed him.

"I knew he'd been floating around and he's very keen to be a professional rugby player, but I was pretty impressed in the trial and timely enough we had an injury."

Scott Sio is unlikely to play in the opening round while Allan Alaalatoa and Jarrad Butler are expected to be available for selection despite failing to play a pre-season trial.

Dewet has had minimal training with the Brumbies but is confident he can slot straight into the side if needed.

But he will continue his day job when he's not training to juggle a double life and live his rugby dream.

"This is it, I've just got to go for it," Dewet said.

"It's not my last chance, but it's a good chance to put my best foot forward at a good age and a mature age.

"The Crusaders have about eight All Blacks. But you get excited about that, it would be a dream come true within a week. I can't wait."

SUPER RUGBY ROUND ONE

Saturday: Canterbury Crusaders v ACT Brumbies at Christchurch, 5.35pm. TV time: Live on Fox Sports 1.