If possible it is best to contain their root systems so they don't invade other plants. I have a 3-4 foot wide strip of land between my patio and a driveway and this keeps the raspberries contained. If you don't have a built-in obstruction to define the bed then I would use some sort of bordering material/root barrier that is at least 6 inches deep to surround the bed. Of course if the bed is surrounded by grass then one can simply mow over the invading canes to keep them at bay. I also use a trellis to keep the canes from flopping all over.