In this case, which is true for most situations, the beams are structural and are mechanically fastened to the roof rafters as part of the roof framing system. Beams can be engineered or dimensional lumber which is later wrapped in finish grade material or, in some instances can be reclaimed or new structural timber. There are some instances where mock beams are added afterwards for design purposes, but any real wood beams will have some weight to them that will need to be supported when installing.