Fowler, the youngest member of the group at 18, and 19-year-old Cooney-Cross are two of the six Olympic debutants named along with goalkeeper Teagan Micah, veteran Aivi Luik and forwards Hayley Raso and Kyah Simon.
"It's a team and a roster that is very attacking balanced, but also with a lot of versatility," Gustavsson said.
"There's a lot of players in this roster that can play multiple positions with which is exactly what you need in an Olympic tournament.
"On the pitch you are definitely going to see a brave team that's going to take a step forward. It's going to be an attacking mindset on the field."
Fowler scored her first goal for Australia earlier this month in a 3-2 loss to Denmark, while Cooney-Cross, who had a breakout W-League season with champions Melbourne Victory, debuted in that international game and then started against Sweden.
Gustavsson also backed veteran midfielder Elise Kellond-Knight to prove her fitness from the ruptured ACL she suffered in July last year.
Kellond-Knight is one of two players in the squad who haven't featured in a game under Gustavsson, along with hard-running midfielder Chloe Logarzo.
The Matildas will play a final tune-up game against Japan on July 14 before their group G matches against New Zealand, Sweden and the United States.
They will be attempting to better their previous-best result, when they were knocked out on penalties in the quarterfinals in 2016.
FULL MATILDAS SQUAD FOR OLYMPICS
Goalkeepers: Teagan Micah, Lydia Williams
Defenders: Steph Catley, Ellie Carpenter, Alanna Kennedy, Clare Polkinghorne, Aivi Luik
Midfielders: Elise Kellond-Knight, Chloe Logarzo, Emily van Egmond, Tameka Yallop, Kyra Cooney-Cross
Forwards: Caitlin Foord, Mary Fowler, Emily Gielnik, Samantha Kerr (C), Hayley Raso, Kyah Simon