Root will make his first outing as Alistair Cook's replacement at the helm when the first Test against South Africa opens at Lord's on Thursday.
White ball specialist Hales, fresh from his unbeaten 187 in Nottinghamshire's One Day Cup final triumph on Saturday, is convinced his England team-mate will thrive with the additional responsibility.
"Joe will be a good captain. He's a naturally aggressive player. He's aggressive when he bats and is always looking to be positive," Hales said.
"Whatever happens, I think he'll always look to take the positive option. When it comes to pressure situations, he's the best guy around.
"He's got a very calm head on his shoulders and I'm backing him all the way to be a very good leader.
"It's going to be a great series, South Africa are one of the best teams in the world but hopefully we can make home advantage count.
"We've played some good cricket over the last few years and I'm backing us to get the job done."
Hales made the last of his 11 Test appearances during Pakistan's tour to these shores last summer and has not given up hope of being involved again, even if he has been overlooked for the South Africa series.
"My Test aspirations are still alive, but at the moment it's a bit restricted on how much red ball cricket I'm playing," Hales said.
"Obviously because of the busy summer we've had so far - because of all the tournaments and one-day series - means we've only played three or four red ball games.
"Whenever I get a chance with Notts I have to keep going and keep knocking on the door."
While England will be battling South Africa over four Tests this summer, Hales will be taking part in the NatWest Twenty20 Blast which begins on Friday night.
"Apart from the T20 games against South Africa last month, I've only played one or two games in the last 14 months since the last World Cup," he said.
"It's a good block coming up so that means I can practise and get my skills back up to where they used to be a couple of years ago.
"The competition's going to change in 2020, but there's still the appetite for Blast in the Notts changing room.
"We had our first T20 training session in Nottingham and the guys were buzzing around and I'm sure that will be the same for the rest of domestic cricket over the next couple of years.
"We've got over the hangover of Saturday and the guys are full of energy."
:: Alex Hales was participating in Major League Baseball's free 'Battlegrounds' event in London's Hyde Park on 4th July. For more information, please visit www.mlb.com/battlegrounds.