Rottnest is the most popular tour destination from Jandakot. You can book yourself one way trip, but a return flight is more economical option. "Rottnest Lunch" departs at 10:00 and flyes back at 14:00 from Rottnest. For a little extra you also can book "Rottnest all day" tour. Some people use this as opportunity to propose and so far they've had 100% success rate. :) If 15 minutes trip in the air each way is not enough for you or you would like to see more, then overflying Perth city before landing in Rotto is the way to go.