"Our first kid was born during filming this and now we're having another one. So if they do a Lowriders 2, I might have a third kid," Rossi joked.
"This film is the best luck. And we feel like there's a lot of good karma, and good luck things happening with it. It's a beautiful story," he added. "We get to build our own family while telling the story of a beautiful family."
Rossi and McDermott -- who welcomed their first child, son Kane, in June 2015 -- said they didn't find out the sex of their baby boy until he was born, and they're waiting this time around as well.
"We were surprised on our son, during the making of this, and we'll be surprised on this," Rossi shared. "You don't get many surprises in life"
The star and his wife said that all they care about is having "a healthy, beautiful baby."
As for their little guy, the proud parents say they don't know how he's going to feel about being a big brother because he's still "super young."
"He's figuring it all out," Rossi said. "We prep him a lot."