Are ent's the surgeons recommended for oropharyngeal cancer? Do plastic surgeons or others get involved?

Yes ENT doctor best. An ENT doctor with good oncology training should by able to remove the cancer and perform any necessary reconstructive surgery. Occasionally, an ENT cancer specialist will work with a reconstructive plastic surgeon in order to work more efficiently or when an unusual reconstruction is required.
Sometimes. Depending on training, ent, plastic surgeons and maxillofacial surgeons are well qualified to perform head and neck cancer surgery. In some cases, a team which includes an oral/maxillofacial surgeon is of value as some surgeries involve the jaw/tongue and neck areas. Chemotherapist and radiotherapists are often consulted in certain type of head and neck cancers.
Yes. Ent surgeons are the best choice for oropharyngeal cancers, usually as the primary surgeon. Howeve, depending on the facility you choose to treat you, you will have your ENT operating very closely with both plastic surgeons and oral surgeons. Much will depend on your reconstructive needs. The team approach, however, is always best.