The Collaborative International Dictionary of English v.0.48:

Roamer \Roam"er\ (r[=o]m"[~e]r), n.
   One who roams; a wanderer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

roamer
    n 1: someone who leads a wandering unsettled life [syn:
         wanderer, roamer, rover, bird of passage]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "roamer":
   Ahasuerus, Ancient Mariner, Argonaut, Flying Dutchman, Goliard,
   Odysseus, Oisin, Ossian, Ulysses, bird of passage, drifter,
   floater, gad, gadabout, go-about, itinerant, mover, peregrinator,
   peregrine, peripatetic, rambler, rolling stone, rover, runabout,
   straggler, stroller, strolling player, troubadour, visitant,
   wanderer, wandering minstrel, wandering scholar