Elisabeth Rohm

Their wedding isn’t until December, but already newly-engaged Law & Order alum Elisabeth Rohm and her fiancé, entrepreneur Ron Wooster, have longterm future plans.

"We absolutely will have a family," Rohm, 34, tells PEOPLE. "I don’t know when, but we’re both hopeful for a family."

But first, the couple are making plans for their honeymoon. "We’ll most likely go to Africa. We have that in common, a fascination with Africa," she said Tuesday. "I think it’ll be a good adventure for us. … We’d like to spend a month there."

Of Wooster 40, whom Rohm began dating in 2005 just after leaving Law & Order, she says, "Our relationship was preordained because we were set up by a really, really good friend of both of ours who knows us really well. About three months in, I think both of us knew. It was love at first sight."

After asking Rohm’s mother for her daughter’s hand, Wooster proposed to the actress recently in their Venice, Calif., home with a five-carat diamond ring set in a platinum band.

Rohm says the proposal was perfect for her down to earth nature. "I was in my pajamas, wearing my glasses, reading, getting ready to go to bed. We were having a really good conversation and he just got on one knee. It was very sweet and very real. How can you say no when you’re in your bedroom?"

Rohm, who left Law & Order after four seasons, will appear opposite Lost’s Terry O’Quinn on the ABC Miniseries Masters of Science Fiction on Saturday.

As for her nuptials, "Originally, we were thinking about throwing a beachy clambake wedding – I have a house in Southampton, [N.Y.], she says. "But then we thought maybe we’d do something wintery, black-tie, in Los Angeles, because a lot of our friends are here."