If the mantle is to be painted like the photo, I would think that the beaded part could easily be made in three pieces - a beaded center and two end blocks, this would give the squared closed ends that I think are shown in the photo. I have one of the Sears molding head cutters and may even have a set of the beading cutters shown. Be aware that there are different beading cutters available, you need to have the set with the narrow outer lip so that the cutter can be indexed across the part to give multiple beads as there is a set out there where the outer lip is much wider than the internal ones. I originally purchased the cutter head and bits to use on a RAS but got really nervous looking at the setup. On a table saw however, with a feather board on the fence holding the material tight to the table and a second holding the material tight to the fence, it should be OK.
Another option would be to use the router bit stated to cut the internal beads, leaving the half round outer bead and then use a scratch stock to cut the two outer half beads. This is a relatively small profile so should be pretty easy to do. Again, I would make three sections so that the beading could have the square ends shown.