The court heard that on August 29, the couple's relationship of two years ended following an argument, when the woman was told to leave.
Two days later, she and a friend went to Rolls' house to pick up her belongings and when the friend asked for her things Rolls told her to send the victim in to get own stuff. But when she did, Rolls told her to leave and threatened to smash her head in, the police summary of facts stated.
When she went back to the car, Rolls began swearing at her and yelled at her to get out of the driveway as his father needed to leave but she refused, stating she needed her wallet, the court heard.
Judge Walsh said Rolls then pushed the five-months' pregnant woman against the car, "pushing the car door into her as hard as he could, hitting her in the chest and jamming her" between the car and door.
"You opened the car door and kneed her in the right leg about six times as hard as you could while holding the roof of the car with both hands for leverage ... this was quite a nasty assault," he told Rolls.
As he did this Rolls called the woman a "hoe" and a "s***", spitting in her face before telling her to leave as he swore at her again, the court heard.
"You were verbally abusive to her and threatened her," the judge said.
Defence lawyer Louise Elder said Rolls had been going through a rough patch at the time of the assault and was remorseful. "His former partner had recently committed suicide ... he is aware any further offending will result in imprisonment," she said.
Judge Walsh noted the pre-sentence report stated Rolls had a moderate to high risk of reoffending. He warned Rolls about further offending and noted he had five previous convictions for assaulting women.
"If you come back to court you may well face a term of imprisonment. If you keep violently offending that will be the consequence ... you need to stop and think about your anger."
Because the pair will soon have a child, Judge Walsh put the protection order in place.
"It's clear there will be an on-going relationship."