Hall endured a dreadful 2008, punctuated by his infamous punch on West Coast defender Brent Staker that led to a seven-game suspension and damaged his reputation.
He was then stood down by the club for two weeks after lashing out at Collingwood backman Shane Wakelin in just his third game back from suspension.
Personal problems were a major factor in Hall's behaviour, which at the time left his playing future in the hands of Swans psychologist Grant Brecht.
But Roos feels Hall, who turned 32 earlier this month, is "in a really good mental space" and ready to recapture the type of form that led to three All-Australian selections and played a big part in the Swans' 2005 flag.
"He finished off the year really, really well," Roos said of Hall who returned to help Sydney reach the 2008 semi-finals, where they lost to the Bulldogs.
"He won our best finals player and that was a credit to him.
"He's really positive around the club, he's training really well, he looks good on the training track.
"He'll play not this week [in the NAB Cup match against Port Adelaide on Sunday] but will the week after.
"So I'm really positive with his season coming up. He seems in a really good mental space and think he's looking forward to the year."
Despite his troubles in 2008, Hall still topped Sydney's goal-kicking list for a seventh consecutive season, equalling the club record set by Len Mortimer between 1906 and 1912.
His 41 majors put him just in front of Swans games record-holder Michael O'Loughlin who booted 36 goals.
Roos still has plenty of faith in Hall's ability in front of goal, but feels his spearhead and O'Loughlin, who is also 32 and still overcoming a major ankle injury, need help for Sydney to remain competitive.
"Hally's got high expectations of himself," Roos said.
"We still rate him very, very highly, but we've got to make sure other players help him out more.
"Naturally when you're getting towards the end of your career as opposed to the start, you're aware at some point that your performance is going to drop off.
"I think this year he'll be fine, the indications are really good, but we need other guys - whether it's (Heath) Grundy, (Ryan) O'Keefe, (O'Loughlin's) performance was fantastic last year - but generally everyone around needs to lift.
"Then it makes Hally's job easier anyway.
"But I think physically and mentally he's in a really good space to have a very, very good year."
