Julie Benz and Rich Orosco
06/27/2011 at 05:00 PM EDT
Actress Julie Benz is taking on a new role: fiancée!
The former Dexter
star, 39, is engaged to her boyfriend of four years, marketing executive Rich Orosco, her rep confirms to PEOPLE.
Orosco, 38, popped the question with a customized Kwiat cushion-cut diamond and platinum engagement ring – complete with a diamond frame and milgrain edge band – on Sunday in the backyard of the home they share in Los Angeles.
"It was absolutely perfect," Benz, who can next be seen on Royal Pains
, tells PEOPLE.
Nearly 60 of their closest friends and family – and a Mariachi band! – helped them celebrate their engagement at a Mexican-style surprise party Orosco planned.
"The proposal was simple and beautiful – and then I was shocked by the pop-up surprise Mexican fiesta engagement party," she says, adding, "What girl doesn't want to be serenaded by a Mariachi band surrounded by close friends and family?"
This will be Benz's second trip down the aisle. She was previously married to actor John Kassir in 1998, but the couple divorced