The couple were in a theater in Aurora, Colorado, watching a midnight showing of "The Dark Knight Rises" with Legarreta's 4-year-old daughter and their infant son on Friday when the gunman opened fire and chaos ensued.
Later, reunited and with the whole family safe, Rohrs proposed to Legarreta, who suffered a minor bullet wound, CNN said.
"He just looked at me and he said, 'I know this is not the time and place, but will you marry me?' And I said, 'Yes,'" Legarreta told CNN host Piers Morgan, discussing her fiance's impromptu proposal.
"Going through 10 minutes of thinking he was dead and I would never see him again, you never want that feeling again," she added.
Police have identified the suspected gunman as James Eagan Holmes, 24. He is accused of opening fire in the crowded theater at a mall in Aurora, killing 12 people and injuring 58 others. Police said 30 people remained hospitalized on Friday evening, 11 of them in critical condition.
"There was a moment where the shooting stopped and I saw people running and at that moment I just grabbed the baby and I just grabbed my daughter and got her out as fast as I could. ... I was just thinking we've just got to get out. I just got to get out the doors and if I just fall dead, just get my kid out of here," Legarreta told CNN.
Rohrs said he lost his 4-month-old son, Ethan, in the darkness and chaos of the theater, but got out himself. Then, once outside, he could not initially find Legarreta.
"I got to my truck and I drove across the mall," Rohrs added. "I'm going to call 911 and trying to call Patricia and it's just ringing, and every time it rings I'm like they're dead, they're dead, your whole family is dead."
"I couldn't think. I got a phone call from a Colorado number and I answered it and thank God it was Patricia," he added.