Final answer:
Pliny the Elder, Ptolemy, and Galen are best described as Roman scientists, known for their significant contributions to natural history, astronomy, and medicine.
Step-by-step explanation:
The best description for the list containing Pliny the Elder, Ptolemy, and Galen is B. Roman scientists. These individuals were not Roman emperors or Hellenistic poets but were renowned for their contributions to scientific knowledge during the Roman Empire.
Pliny the Elder was a naturalist and author known for his encyclopedic work 'Natural History'; Ptolemy was a prominent astronomer and geographer, famous for his work 'Almagest', which was a compilation of astronomical knowledge; Galen was a distinguished physician and surgeon whose understanding and practices influenced medical science for many centuries.