means Wandering or moving freely over an area without a fixed route, and in modern usage, using your phone on a network outside your home carrier's coverage.

from From the verb 'roam,' which surfaced in Middle English as 'romen,' meaning to walk or wander about. Its deeper roots are murky — a popular tale links it to medieval pilgrims heading to Rome (Old French 'Romier,' a Rome-bound traveller), but scholars treat that connection as folk etymology rather than fact. The wandering sense is old; the telecom sense, where your phone 'roams' onto another network and bills you for the privilege, is a late-20th-century gift from the mobile age.